I N D U S T R I A L A N D ENGINEERING CHEMISTRY
Januarv. 1926
85
Vitamins in Canned Foods' IV-Green Peas By Walter H. Eddy, Edward F. Kohman, and Victoria Carlsson TEACHERS COLLEGE, COLUMBIA UNIVERSITY, NEWYORK, N. Y., AND NATIONAL CANNERS ASSOCIATION, WASHINGTON, D. C.
HIS report is the fourth
T
in a series2 of' joint researches to establish the vitamin values of canned foodstuffs. During the past year (1924) about nineteen million cases (of twenty-four No. 2 cans each) of peas were canned in the United States. So large a production and consumption of a single foodstuff calls for accurate data as to vitamin value. The methods of inrestigation have already been outlined in the preceding papers, but in this particular investigation the studies have been extended to include not only vitamins A, B, and C, but also
results of intakes that were close to maintenance rather than to normal growth. During the past few years Sherman and his co-workers have developed a technic for both vitamin A and B measurement which is based on this principle and which has already given us certain basal values for comparison. I n t h e s t u d i e s here reported use has been made of this technic. The stock rats are raised on Sherman's Diet 13, which consists of two-thirds ground whole wheat, one-thirdwhole milk powder, and sodium chloride equal to 2 per cent of the whole wheat used. Litters from this stock were taken a t the age of 30 days and placed on a vitamin A-free diet composed of 18 per cent extracted casein, 74 per cent extracted cornstarch, 4 per cent Osborne and Mendel salt mixture, and 4 per cent dried Fleischmann yeast. As soon as these animals attained a period of definite decline in weight ,,f curve it was assumed ---- -_that they were A-free. I Such a condition re/NrA'AH€ 50#g. r loo$ quired an average of about 65 days on the above diet. At this point the foodstuff to be tested was added to the diet, being fed in definite a m o u n t s i n u separate d i s h e s w i t h the basal diet ad lib. Munsel13 used this technic and selected a /N TA KE 250 ti-7 4gain of 25 grams per Chart 11-Vitamin A Studies. Effect rat in the 8 weeks fol- of Variation in C a n n i n g Process u p o n A Content. Canned M e d i u m lowing attainment of Vitamin Sized Peas Used (No. 3) I-Raw ungraded peas (control). II-No. A-freedom as a basis 3 peas blanched 7 minutes and rocessed 25 for comparison of a minutes at 120° C. (248'F.). IIP-No. 3 peas 25 minutes at 120" C. (248O F.) but n u m b e r of different processed nof blanched. IT.'-No 3 peas blanched 7 foodstuffs. Butter. for minutes and processed 50 minutes at 120° C. ' (248O F.). e x a m p l e , she found Intake figures give milligrams of peas fed adequate to this pur- per rat per day: weight scale 20 grams per division. pose in amounts cited as 20 mg. per day per rat. On Charts I and I1 are shown the results of feeding 25, 50, 125, and 250 mg. of green peas daily per rat and the resulting gains in a 60-day period. Using ungraded raw green peas purchased daily in the New York market 25 mg. daily were found inadequate
Green peas are to be ranked as a rich source of vitamins A, B, and C, but evidence of D is lacking. Maturity, reflected in size, results in reduction of A and C and increase in B, small peas being richer in A and C and poorer in B than large peas. No cooking or canning process affects appreciably the content of vitamins A and B and, as shown in previous work, canning is less destructive to the C content than is kettle cooking, probably because of the exclusion of oxygen in the canned product. Compared with other sources of vitamins, canned peas are, roughly, at least half the value of butter as a source of A, they are richer in B than milk, tomatoes, or oranges, and about as rich as tomatoes and oranges as a source of C. Blanching is relatively more destructive than processing. Reheating canned peas in an open kettle for serving upon dumping - them from the can does not materially reduce the vitamin C content.
D.
Vitamin A Content
In earlier studies of vitamin values it was customary to aim a t the amount necessary or adequate to normal growth. I n many papers the conclusions stated that the "following amount results in normal uowth" without attempting - to determine the minimum protective dosage of that particular foodstuff. Such data make quantitative comparisons difficult. A few years ago J. C. D r u m m o n d s u g g e s t e d that INTAKE 25 m4. 100 when growth curves were to be used as criteria for vitamin value more accurate comparisons of different foodstuffs, or of varying amounts of a given foodstuff, were obtainable b y comparing
-
Chart I-Vitamin A Studies. Individual Gains of White R a t s o n Varying Intakes of Green Peas as Source of Vitamin A during a 60-Day Period Following Clearance of Stored A. I-Raw ungraded peas. II-Ungraded green peas cookedinkettlefor 12to 15minutesal 100°C.(212OF.) (home cooking). IlII-Canned small peas (No. 1). IV-Canned medium peas (No. 3). V-Canned large peas (No. 6). Intake figures give milligrams of peas fed per rat per day; weight scale 20 grams per division.
1 P r e s e n t e d in part before a joint session of the Divisions of B i o l o g i c a l Chemistry and Agricultural and Food Chemistry at the 69th Meeting of the American Chemical Society, Baltimore, Md., April 6 to 10, 1925. * THISJOURNAL, 16, 52, 1261 (1924); 17, 69 (1925).
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,,/- _ _ _ _
8
Dissertation, Columbia University, 1924.
Vol. 18, KO. 1
INDUSTRIAL AND ENGINEERING CHEMISTRY
86
for a 25-gram gain in 60 days, but 50 mg. produced this result. The ungraded raw market peas may therefore be assumed to be about half the value of butter as a source of vitamin A . Cooking such peas on the stove for 12 to 15 minutes at 212' F. (100' C.), shows little destructive action on the vitamin, 50 mg. daily being still nearly adequate for the standard growth rate selected (Column 11, Chart I). When the equivalent of the intakes of raw peas is fed in graded canned peas, two results are notable. First, it seems safe to state that any size of canned pea will be about half the value of butter as a source of A, but that the smaller peas (No. 1) are apparently richer in vitamin A than the more mature peas (Nos. 3 and 6). This is emphasized more in the appearance of the animals than in the growth curves (Columns 111, IV, and V, Chart I). The canned peas reported in this test were of three sizes. Since peas for canning are harvested by mowing the vines and shelled mechanically in a viner, t h e grade is a n index not only ofLsize but also of the degree of maturity. The following details in-regard to the canning should be noted: No. 1. (Petit pois) blanched 5 minutes, processed for 25 minutes at 120" C. (248" F.)in No. 2 cans. No. 3. (Medium size) blanched 7 minutes, processed 25 minutes at 120' C. (248" F.). No. 6. (Large or marrow-fat type) blanched 10 minutes, processed 25 minutes at 120° C. (248" FJ.
Chart I1 shows a study of the effect of certain variations in process. using No. 3 canned peas and contrasting with ungraded raw peas. The variations in process studied were the effect of omitting the blanch and doubling the cooking time. The curves together with direct observation of the animals' condition as to coat and other physical factors indicate that neither the blanching nor the extra heat produces any appreciable reduction in vitamin A value (Columns 11, 111, and IV, Chart 11). Since 125 mg. daily of any of variants results in greater than 25 grams gain in 60 days, and in the case of numerous test animaIs 50 mg. produces this result, it can be assumed that within these variations canned peas are one-sixth to one-half of the value of butter as a source of vitamin A and that peas as ordinarily canned come closer to the half value than to the sixth value. Canned peas, therefore, are a n excellent source of vitamin A, for in comparison with other foods tested by Munsell, the writers' results show them to be richer in A than string beans, lettuce, tomatoes, or orange juice, about equal to carrots, and surpassed by butter, cod-liver oil, egg yolk, and spinach. Vitamin B Content
Comparative data were sought a t intakes which varied over a range sufficient to produce less than normal growth a n d m o r e than maintenance. These intakes made it possible 100-DAY GA INS t o c o n t r a s t different forms of peas and to make a comparison with the work of Sherman and co-workers. The comparisons with these workers are not absolute, as the present writers adopted the procedure of Osborne and Mendel and first prod u c e d a w e i g h t decrease by about 2 weeks' feeding of a vitam i n - f r e e diet and then introduced the B source fed separ a t e l y f r o m t h e basal diet. These tests are the more severe, I therefore, as they represent the I GUAM ' P E A S effect of restoration to growth h I X as well as maintenance of the rate reported. I n the Sherman studies cited in comparison the 0 2 experiments varied from these in that the B sources were intro100 duced a t the 28-day period and b there was no preliminary B-free treatment
The intermediate sizes 2 and 5 were not used in this test.
60-DAY GAINS
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3 INTAKE
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0 Chart 111-Vitamin B Studies. Individual Gains of White R a t s on Various Kinds a n d A m o u n t s of Green Peas as a Source of Vitamin B during a 60-Day a n d a 100-Day Period I-Control obtained by using 0.3 gram daily of dried bakers' yeast per rat as source of vitamin B. 11-Raw ungraded peas. IIZ-Ungraded peas cooked in kettle 12 to 15 minutes at 100' C. (212'F.) (home cooking). I V-Canned No. 1 peas. V-Canned No 3 peas. VI-Canned No. 6 peas. Intake-figures give the grams of peas per rat per day. weight scale 20 grams per division.
I
The basal diets were practically i d e n t i c a l . Sherman's Diet 107 c o n s i s t s of casein 18 per cent, starch 68 per cent, Osborne & Mendel salt mixture 4 per cent, butter fat 8 per cent, and codliver oil 2 per cent; while a diet used by the writers consisted of 18 per cent extracted casein, 68 per cent starch, 4 per cent OSborne & Mendel salt mixture, or i'vkcollum 185, 10 per cent butter fat (or 5 per cent fat and 5 per cent cod-liver oil).
Using Diet 107, Sherman and S p o h n 4 r e p o r t a gain of 15 4 Spohn, Dissertation, Columbia University, 1922.
January, 1926
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I X D VSTRIAL A N D ENGINEERING CHEMISTRY
grams per rat in 56 days on 6 cc. of unheated milk as a source of vitamin C values of green peas (Charts V and VI). Guinea of vitamin B, and 40 grams on 8 cc. Sherman and Grose5 pigs were put on the experimental diets when they had reached report that unheated tomato juice produces 21.4 grams a weight of approximately 350 grams. During this experigain per rat in 10-cc. daily doses in a period of 56 days. ment the same batch of skim milk powder was used throughThese figures give comparative data for the results with out and the writers had occasion to confirm by over forty-five control tests the absence of C in their basal diet (Sherman-green peas. On Chart I11 is shown a comparison of growth gains during LaMer formula6) and its power to produce death by scurvy 60-day and 100-day periods of rats on-various sizes IO0 -DA Y GAINS of raw, home-cooked, and canned peas. One result 60-DAY GAINS soon established itself-i. e., that the more mature the pea in the range studied, the richer the content in B vitamin. No. 6 size (large) is uniformly richer than No. 1 or No. 3 size. The relation of B and -4to size is therefore exactly reversed, B increasing with maturity and A decreasing (Chart 111, Columns IV, V, and VI). I I1 0 I n the case of canned No. 6 peas the requirement INTAKE 2 GRAMS for normal growth is approximately 5 grams daily, 100 whereas the requirement for 20 grams gain per rat in 60 days in contrast to normal growth is about 2 grams. Two grams daily of raw ungraded peas average better than 20 grams gain per rat in 60 days, and 2 grams 0 % canned No. 6 compare favorably with the raw variety I80 1 at this intake. This relationship is confirmed by feedL ing at a 3-gram level and contrasting 60- and 100X day feeding tests (Chart 111). I n comparison with the tJ Sherman results this would indicate the following 100 iii approximate equivalents: 5
rl
Approximate Equivalents FOODSTUFFS Unheated milk Unheated tomato juice Raw ungraded green peas Normally canned No. 6 peas Normally canned No. 3 peas Normally canned No. 1 peas
AYOL'NTS
6 cc. 10 cc. 1 to 2 grams 2 grams 2 to 3 grams 2 to 3 grams
1111
3 ? I80 q u 0
IO0 That blanching is relatively greater to be feared as a reductant of vitamin B content than variation in heating is brought out in Chart IV. Single and double heated No. 3 canned peas show little difference in B 0 content a t any level of intake tested (3, 4,or 5 grams). (Chart IV, Columns I1 and 111) By omitting the /NTAKP 5 GRAMS blanch but retaining the process, No. 3 canned peas Chart IV-Vitamin B Studies. Effect of Variation in Canning Process upon Vitamin B Content of No. 3 Peas become the equivalent of the raw ungraded peas. (Chart I-Control using raw ungraded peas. 11-No. 3 peas blanched 7 minutes and processed 2.5 minutes at 120" C. (248O F.). 111-No. 3 peas blanched 7minutes but IV, Columns I and IT.') processed 50 minutes at 120° C. (248O F.). IV-No. 3 peas processed 25 minutes To summarize, green peas are richer in vitamin B at 120' C. (248' F.) but nof blanched. figures give the grams of peas per rate per day; weight scale 20 grams content, weight for weight, than either milk or tomato perIntake division. juice. More mature peas are richer in vitamin B than small immature peas, No. 1's and No. 3's being roughly on an average of 30 to 35 days. Using this basal diet, two-thirds the value of No. 6's. There is no appreciable de- the writers had included in their studies the evaluation of struction of B value in peas by home-cooking.or in processing vitamin C in raw, home-cooked, and canned peas of various of canned peas, but the duration and method of blanch is a sizes, the effect of heat, blanch, and other variants in process, factor and should be reduced as much as possible to conserve and the effect of the reheating necessary to serving canned the full value of this factor. Using a 10-minute blanch for peas. No. Us, a 7-minute blanch for No. 3's, and a 25-minute Two grams daily of ungraded raw green peas from the city process at 120" C. (248' F.) (a normal commercialIpractice), market is protective against scurvy in guinea pigs for periods No. 6's are the equivalent and No. 3's are about two-thirds of 90 days. One gram daily is not protective. If these the equivalent of raw ungraded peas. ungraded peas are cooked in a kettle for 12 to 15 minutes at 100' C . (212' F.) (home-cooking), 5 grams are protective but Vitamin C Content 3 grams fail to protect. Normally processed No. 1 and No. 3 Previous reports in this series have confirmed the con- peas protect in 3-gram doses and give growth results comparatentions of other workers in this field that the destruction of ble to 2 grams of raw ungraded peas, whereas 4 grams of vitamin C is greatly reduced by removing the possibility of canned No. 6 peas are necessary to attain similar results, oxidation. A corollary of this has been to show, in the case Vitamin C, therefore, like A and unlike B, is more abundant of cabbage and spinach, that canned foods lose less vitamin in the immature than in the mature peas. When correlated C in the commercial process than do the same foodstuffs with the vitamin C studies already published by the under home-cooking, the latter permitting free access of oxy- writers, the relative position of green peas as antiscorbutics gen. These results are extended and confirmed by studies seems to be established, as shown in Table I. 6
J . Am. Chrm. SOL., 45, 2728 (1923).
'Sherman, LaMet, and Campbell, J . Am. Chem. Soc., 44, 103 (1922).
INDUSTRIAL AND ENGINEERING CHEMISTRY
88
Peas, therefore, rank as one of our richest antiscorbutics. The close similarity of Columns I11 and IV, Chart VI, indicates that the effect of blanching in commercial canning is detectable but not pronounced. With 2 grams intake the unblanched peas gave somewhat better results, but with 3 g a m s intake blanched and unblanched were alike. This blanching is continuous in boiling water, which, as a result of constantly boiling, is relatively free from oxygen. The close similarity in the growth curves and appearance of the pigs represented in Columns V and VI, Chart VI, shows that extending the commercid process from 25 to 50 minutes produces very little if any noticeable further destruction of vitamin C. This is in harmony with the results on canned cabbage, apples, and spinach.% Column VII, Chart VI, shows considerably less v i t a m i n C in 3 I T m w - v p7 'po h o m e - c ooked peas t h a n in canned peas.
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C h a r t V-Vitamin C Studies. Individual G a i n s o r Losses of G u i n e a Pigs on Various Int a k e s of G r e e n P e a s as a S o u r c e of V i t a m i n C. The gains of protected pigs were for a period of 90 days Pigs which on autopsy showed scurvy are indicat'ed by the letter (s), those dying of scurvy by the letters ( d s ) . Less than 3 grams daily were not fed except in the case of raw peas, and one lot of canned peas. None of the pigs receiving 3 grams of the various lots gave any evidence of having scurvy. The approximate weight of t h e pigs at the timeof starting the experimental diets was 350 grams I-Controls on basal diet alone. I I i R a r r ungraded peas. 111-Canned No. 1peas. IV-Canned No. 3 peas. V-Canned No. 6 peas. VI-Home-cooked ungraded eas Intake lgures give grams of peas per day; weight scale 100 grams per division.
t i e r e s u l t s on the three abovementioned foods. Certain canned foods are prepared for t h e table by heating. Sometimes this is done before opening the can, but more often the heating is done i n a new container. Impressed with the v i e w p o i n t that oxidation rather than heat is the destructive factor for vitamin C, and knowing by e x p e r i m e n t that shortly after canning the contents of a can are oxygen-free, the writers have believed that when n can is opened and its contents dumped into a kettle to be warmed for the table they would not absorb enough oxygen in that time to produce m u c h d e structive effect. To remove this m a t t eI f I Om s p e c u l a t i o n to evidence, One ries O f experimentS (Chart VI, Column V) is reported where the contents of a can
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C h a r t VI-Vitamin C S t u d i e s . Effect of Variation i n C a n n i n a Proce s s upon V i t a m i n C C o n t e n t of No. 3 P e a s I-Controls on basal diet alone. II-Control on raw ungraded peas. III-No. 3 peas rocessed 25 minutes a t 120' C. (248'F.) but not blanched. IV-Same as but blanched 7 minutes. V-Removed from can and brought t o boiling in kettle representing table preparation. VI-Blanched 7 minutes but processed 50 minutes at 120' C. (248' F.). VII-Ungraded peas cooked in kettle 12 t o 15 minutes at 100' C . (212" F.) (home cooking). Intake figures give grams of peas per plg per day; scale 100 grams per division.
18
of normal process No. 3 peas after pouring into an open kettle were raised to a temperature of 100" C. (212' F.) and maintained there for 2 minutes before feeding. There may be a slight decrease in vitamin C as a result (contrast Columns V and IV, Chart VI), but this treatment still leaves 3 grams a protective dose. The reheating of canned peas, therefore, is not comparable with the effect of cooking raw peas, for in the canned product we start with an oxygen-free product. Protective Doses of t h e G u i n e a Pig Dose FOODSTUFFS Grams 1.5 t o 3 Orange juice 2.5 to 3 Tomato juice Raw cabbage I Canned cabbage 4 to 5 Home-cooked cabbage 20 Raw a m l e s 10 . Raw a'pples 10 to 20 Canned apples (without reMore than 45 moval of oxygen) Canned apples (oxygen removed by brine immer20 sion) Raw spinach 0.25 to 1 Canned spinach Less than 4 Home-cooked spinach More than 10 Raw ungraded peas 2 Canned No. 1 peas (small) 3 Canned No. 3 peas (medium) 3 Canned No. 6 peas (large) 4 5 Home-cooked ungraded peas Canned No. 3 peas reheated for table 3 Table I-Minimum
It
A n t i s c o r b u t l c s for AUTHORITY
I Various authors Givens and McCluggage and LaMer .Sherman ~
. .
Delf, Eddy, etal. ~ - Eddy, Kobman Eddy, et al. Givens and McCluggage
Kohman Eddy, CarlssAn
and
This paper
Vitamin D
The foregoing results indicate that peas in any form are relatively rich sources of vitamins A, B, and C. Do they
January, 1926
INDUSTRIAL A N D ENGINEERING CHEMISTRY
also contain D, using this letter to designate the antirachitic factor? Hess’s experiments with spinach led the writers to expect a negative result, and this expectation was confirmed by experiment. Two groups of 30-day rats were selected. For a period of 45 days (controls) Sherman and Pappenheimer’s diet 84 (a rickets-producing diet) mas fed to one group. The second group also received Diet 84, but in addition 3 grams of peas daily. At the end of 45 days Diet 84 was replaced in both groups with Pappenheimer and Zucker’s Diet D (containing butter and casein). At the end of 55 days all rats were chloroformed, the blood analyzed for inorganic phosphate, and the rib junctions sectioned for rachitic symptoms. The rachitic diets were improved as growth stimuli by addition of peas, but rickets on these diets was quite as severe as in the controls. There is then no evidence of the
89
presence of vitamin D in green peas a t the level of intake used. However, since rachitic tendencies are enhanced by an increased rate of growth it is still possible that peas contain a small amount of vitamin D which was not manifest because of the demand created by the increased growth rate. Table 11-Effect
of Feeding Peas on Inorganic Phosphorus in Blood Chin nn .~. Oiin on -.-
SEX
Male Female Female
Diet 84 in 45 days Grams
Diet D Inorganic in 55 days phosphorus Grams Per cent Grou9 I-3 grams Deas daily 25 45 1.5 21 34 2.15 32 35 2.53
Group II-No Male Female Female
5 2 8
AUTOPSY Rickets Rickets Rickets
p u s , controls 5 0
7
2.14 3.01 2.14
Rickets Rickets Rickets
Jelly Strength of Pectin Jells’.’ By George L. Baker ~ 7 N l V E R S I T YO F
DELAWARE EXPERIMENT STATION, NEWARK, DEL.
Jelly strength as determined by the device described is shown to be influenced by several factors. When quantity of acid is considered, optimum points of jelly strength for pectin jellies follow Tarr’s 1 :2: 3 ratio for sulfuric, tartaric, and citric acids. However, the relative strength of the optimum points varies for the various acids. Also the pH of the optimum points varies slightly. A 69.44 per cent concentration of sugar produces the maximum jelly strength for a pectin jelly with 1 gram of pectin. With an increase in the concentration of pectin to 2 grams the optimum jelly strength appears at a 66.66 per cent concentration of sugar. A definite pectin-sugar ratio must be maintained for a certain pH in order to obtain a jelly of optimum strength. *
Jelly strength increases with an increase in pectin concentration. An optimum concentration of pectin at 0.97 per cent of the weight of finished jelly is apparent, beyond which cloudiness and an undesirable texture appears. Concentration of pectin in presence of acids before adding sugar is detrimental to jelly strength, while boiling after the addition of sugar has a negligible effect. Thus an increase in invert sugar has no harmful effect upon jelly strength. Decreasing the temperature of a jelly increases the jelly strength. A pectin jelly increases slightly in strength while standing for a period of time at a temperature of 22O
c.
. .. . . . . , , ., . .
EW physical measurements have been recorded on jellies made from fruit juices or pectin solutions. Past
F
methods of measuring jelly strength have been approximate, especially when the comparison was made by the “finger test”-the resistance of the jelly to the finger. The observations recorded have been accordingly in inaccurate terms, such as tender, good, tough, etc. The object of this paper is to describe a n apparatus which is especially adapted for measuring the strength of pectin jellies and to present a discussion of some of the factors of jelly strength as determined by the device. Jelly Strength Tester
After several of the testers for glues and gelatins on the market were tried, none was found to be satisfactory for measuring the strength of pectin jellies, because they are much more tender than glues or gelatins. Consequently, an instrument was devised for measuring jelly strength which proved satisfactory in this work and which is easily adapted to stronger jellies by using a heavier liquid in the manometer. The principle of the apparatus is simple; 1 Presented as a part of the Pectin Symposium before the joint session of the Divisions of Agricultural and Food Chemistry and Biological Cnemistry with the Division of Sugar Chemistry at the 70th Meeting of the American Chemical Society, Los Angeles, Calif., August 3 to 8, 1925. a Based on experiments of jelly strength factors performed at the Delaware Agricultural Experiment Station by I,. W. Tarr and G . I,. Baker. A complete account will be published later in bulletin form.
pressure is developed by the displacement of air by water in a bottle and transferred to a syringe chamber and manometer, forcing the syringe plunger into the jelly and recording the energy required on the manometer. This device is shown in Figure 1. A is the inlet for water to the 2-liter Woulfe bottle, B. Cis the outlet for air pressure developed. D is a 3-way stopcock, outlet E bringing the system to equilibrium, outlet F transferring the pressure to manometer G (30-cc. bulb) and to the plunger chamber above the plunger H . I is a heavy rubber connection. J is the manometer scale. K is a stopcock controlling the overflow of water from B through L. The plunger H and container is an ordinary 10-ml. Luer syringe, the thumb-piece being used to penetrate the jelly. No lubricant is used between plunger and container, as it is a groundglass joint and air-tight. The manometer G contains water colored by a red dye. The scale is in centimeters, 0 to 150. The glass tubing used in the connections to the Woulfe bottle is 5 mm. in outside diameter, that for the manometer scale tube is 4 mm. in outside diameter. The area of the thumb piece of the syringe coming in contact with the jelly is 2.836 sq. cm. There are two ways of regulating the pressure availableby changing the height of the water in B or by regulating the flow from A . The flow of water is slow, about a hundred drops per minute. The pressure is always regulated so that the manometer registers 30 at the end of one minute
