Red Squill Investigations Properties, Toxicity, and Palatability of Red Squill and Powder Baits to Rats
Coiritoey.
U.S. Burcnu 01 Bialoyieal
Slrrnsy
A RED SQUILL BULB
a powerful emetic and, if eaten by maa or aiiinialv other than rats or mice, causes severe vomiting. The squill is relatively
hl. G . O'CONNOB, H. E. BUCK, AND C. R. FELLERS Muubnchusetts; State College, Amherst, Mass.
HR
ED SQUILL is known botanically as Lkgineu nzaritima. It is a pereniiial plant
nontoxic to poultry. Rats do not vomit and hence are poisoned. Red squill has been extensively employed for several years in this country and alxoad by bot11 public and private agencies for the destruction of rats and mice. The U. S. Biological Survey has been particularly active in its use. Since red squill powders vary greatly in toxicity, a reliable niethod for standardizing these powders is necessary. Because the toxic principle of red squill is not definitely known, a chemical procedure as a means of standardizing red squill cannot be used. It is necessary to resort t o a biological procedure, using white or possibly wild rats as laboratory animals. Claremont (1) md Munch, Gilver, and Horn (3) noted that less squill is required to kill wild rats than white rats. Eowever, since wild rats are not easily obtained for hboratory work, the results attained by using white rats h w e proved satisfactory. The following method for toxicity determination is essentially that described by Munch, Silver, and Ilorn (3).
which grows wild on the coasts of southern Italy, Sicily, Sardinia, and other Mediterranean countries. The large bulbs are pear shaped and from 15 to 30 em. (5.9 to 11.8 inches) in diameter, atid t.hey weigh froni 1 to 6 pounds. The bulbs consist of closely overlapping fleshy scales somewhat resembling an onion. The outer scales are Standardization of Red Squill Powders dry, brittle, and reddish brown. The inner scales vary from The rats should be healthy, Strong, young animals weighing 100 a light creamy color to deep purple, while the central scales to 175 gram. The rats are first weighed and phbced in indiare usually white. The plant bears a flowering stern and vidual cages. They arc deprived of food for ap roximatcly 16 leaves a t different periods of the year. hours but are given water. This procedure is fofiowed so as to insure a somewhat constant appetite and tu favor a rapid and Both wild and cultivated bulbs are collected in August comolete consumution of t.he exuerimental diet. and September and, after the ronioval of roots and dry outer scales, are cut into slices transversely and are then either sundried or oven-dried. The oven-dried bulbs are preferred because a more uniform tox__._______________~icity is obtained. Munch, Silver, and Horn (8) of the Red squill powder prepared from the bulb Urginea muritimu is an ideal U. 8. Biological Survey in and specific raticide. The nature of the rat-killing principle is unknown. 1929 summed up the i n f o r m A simplified method of biological assay using white rats is described. Large t.ion on red squill aud its use a s a raticide. Practical rats require higher Concentrations to kill. In general, sun-dried squills are methods of bait preparation less toxic than dehydrated. Rats, recnvered from a sublethal dose of squill, and distribution have been will not eat the powder again but will repeatedly consume sublethal feedings s u g g e s t e d b y S i l v e r (4). of baits containing aleohol or glycerol extracts of squill. They found that bulbs dried Rats prefer baits prepared from meat, fish, or cereal. Various essential in ail oven a t a constant temperature of 80" C . prooils will not cause inaxcased bait consumption. duce a powder of more uniCanned red squill bait formulas were worked out and used extensively in formtoxicity than bulbs dried field tests with effective results. The toxicity of red squilI powder is not under different conditions. affected by the heat of the canning process. The advantagesof canned readyRed squill powder is permixed, red squill bait are obvious. haps the only safe, yet effee--_~____ tive, rat-killing agent. It is 1377
VOL. 27, NO. 11
INDUSTRIAL AND ENGINEERING CHEMISTRY
1378
tabulation of results obtained in determining the toxicity of a red squill powder. Laboratory or commercially prepared red squill extracts can also be assayed for toxicity by feeding equivalent amounts of extract. A definite quantity of extract is added to the laboratory rat ration, which is then fed t o rats a t several levels.
A simple method of expressing results is represented in Table 11. The limited data in this table show that large rats areless susceptible to the toxic effects of red squill than smaller ones fed simultaneously with them. In general, the observations indicate that rat's weighing over 200 grams require considerably more red squill than is required by 100-gram rats. In Table I1 the factor is 1.8. Additional data were collected on the effect of size of inale rats on the relat'ive toxicity of red squill preparations. These figures were collected over a period of several months and, in some cases, may not be strictly comparable. However, they add weight to the writers' repeated observation that large rats are more resistant to red squill per unit' body weight than small ones:
Keight of Male Rats Grams Below 175 (av. 135) Above 175 (av. 240)
~
--------Feeding -500 mg./kg.-No. rats % fed killed 237 118
Level-------750 mg./kg --. No. rats % fed killed
65.4 43.3
115 88
78 2 54.5
Courtesy, G. S . Bureau of Biological Surcey
Ak TYPICAL POTTEDRED SQUILLP L . ~ - T The bulb weinhs about 5 pounds.
of red squill powder t o be assayed is weighed and then thoroughly mixed with this ration in the proportion of one part of squill powder to ten parts of ration. This ratio is used to insure, in most cases, a thorough clean-up by the rats. A rat will normally consume about 1 per cent of his body weight in food per day. The weighed squill ration mixtures are placed in the cages in shallow glass containers. The time when these containers are placed in the cages is noted, and frequent inspect'ions are made to determine the time at which all of the food has been consumed. As a general rule the food is readily eaten in a few hours. The dish is then removed and the rat left without food for 12 hours. The animals are examined daily for 3 days, their conditions noted, and the dead are removed. After the first day, survivors are offered the regular diet. A11 rats that die within 3 days are considered to have been killed by squill. Table I shows a typical TABLE
I. TYPICAL REDSQUILL TOXICITY &3sAY
(Feeding level, 350 mg. of powder Rat Bait Squill No. Weight Fed Fed Grams Mg. Mu. 31 1 91 310 34 340 2 98 36 3 103 360 400 40 4 116 480 48 5 139 460 46 6 142 50 7 144 500 51 8 148 510 590 59 9 171 670 67 10 192 68 11 196 680 75 12 217 750 107 13 308 1070 113 14 323 1130
per kg. of body weight) Bait Squill Eaten Eaten Results Mg. Mg. 310 31 Dead 340 34 Dead 360 36 Dead 40 Dead 400 48 Sick 480 46 Dead 460 500 50 Sick 510 51 Dead 59 Dead 590 67 Sick 670 68 Dead 680 75 Sick 750 107 Sick 1070 113 Sick 1130
O F REDSQUILL TABLE 11. EFFECTOF SIZEOF RATozi TOXICITY
POWDER ~
Feeding Level per Kg. Body \Tt.
--Size 85-175 grams
My.
250 300 350 400 450 500 550
1/9a 6/9 7/9 9/9 7/9 8/9 3/3
of Rat----. 175-400 grams
~~
Feeding Level --Size per Kg, 85-175 Body W t . grams MO. 600 7 00
750 800 850
Si4 ... ... ...
Approx. LDIo
450
of Rat175-400 grams
Numerator of each fraction s l i o a s number of rats dying aithin 3 days; ' ' , denominator ehoxs total number of rats fed indicated dose. a
Lethal Dose for Rats The lethal dose is selected as the smallest amount of red squill powder, in milligrams per kilogram of body weight, that kills a t least 80 per cent of the rats within 3 days and is referred to as LD,, in this paper. This is an arbitrary figure but one which seems to be in accord with experimental toxicity data. Rats vary considerably in their resistance to red squill, and the results of toxicity determinations will vary somewhat on repeat tests. With reference to Table 11, LDs0 for ratq weighing 85 to 175 grams is 460 mg. per kg. and for rats weighing from 175 to 400 grams, approximately 825 mg. per kg. Assay of Commercial Red Squill Preparations
A considerable number of red squill preparations were assayed by this rnethod as shown in Table 111. Red squill powder which had been in storage for 3 years showed no deterioration. There was considerable variation in toxicity among the preparations examined. Attention is called t o the large relative variability in reaction of groups of rats a t different feeding levels. This inconstancy of the experimental animal niakes necessary the use of a large number of rats a t each of several levels of feeding. The only sun-dried powder examined was of the usual low toxicity of these sun-dried squills. Overdosage of red squill produces the same toxic effects as minimum lethal dosage.
Palatability of Baits for Rats That rats have decided food preferences is well known. Obviously, in baiting rats it is desirable to use the most effective attractants possible. To this end approximately four hundred feeding tests were carried on to determine the relative palatability of many foods, such as grains, cereals, fresh, canned, a n d d r i e d meats and fish, dried milk, b r e a d , a n d many others, b o t h separately and with added red squill powder or extracts. Details of these e x p e r i m e n t s will not be given here. In general, the method consisted in placing
NOVEMBER, 1935
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLE111. TOXICITY O F TWELVE COMMERCIAL RED SQUILL
Feeding Level per Kg. Body Powder
wt.
M g. 2 50 300 350 400 450
500 550 600 700 750 800 850 900 1000 2000 Appror. LDm
2/15 6/15 5/15 10/15 9/15 10/15 5/12 6/9 16/18 7/9 6/9 9/9
...
Powder 2 Stored Powder 3 I'rs 3
...
...
. .
...
...
...
... ...
... ...
Powder 5
Powder 6
Powder 7
...
v.
5/10
2/10 1/10
...
3i5
9/10
...
5/5
.
...
b
... , . .
, . .
...
015
,515
9i9
si18
... 6;s
5;5
s;i 10/10 ...
3jio
iojis ... ...
4/5
,..
9/15
5;s
4;5
... ... ...
...
... . . . . ,..
...
..
,
.
... 400
...
...
... ...
... ... ...
...
...
... ...
6/8
...
450
900
+
...
5/5 , . .
... ...
SUMMARY O F COOPERATIVE
...
, . ,
...
... ... ...
...
5/ia
450
400
...
...
RAT ER.4DICATION Fresh Bait, 1930-1931 38 6 21,777 15,648 4,565 29 2 3,104 685 81.9 2,557 1,744 59.5 2,832 1,670 27 ._ ..1 6,466
3,762 439 10.5 1,581 $48,353.16 $30.60
...
5/10
.,.
...
1000
+
Extract 1
Extract 2
Extract 3
...
... . .
. . ...
i/i
...
SunDried Powder
. .
...
...
7/9
No. of county-wide campaigns Other campaigns (less t h a n county) Packages of 3-can bait distributed N o . rept. cards sent t o cooperators No. rept. cards returned Per cent of return No. reporting satisfaction No. reporting not satisfied Per cent satisfied No. reporting no live r a t s left No. reporting live r a t s left Per cent reporting no live r a t s left No. reporting no dead rats f o u n d No. finding dead r a t s Per cent finding dead r a t s No. of dead r a t s found No. reporting no odor No. reporting odor Per cent reporting odor N o . reporting r a t damage Total amount damage reported Av. yearly damage (those reporting) IL
Powder 9
...
,
in each cage two or three dishes containing 20 grams each of the foods being tested. The rats are normally fasted overnight and given t'he choice of foods in the morning. The food dishes are left in the cages for 4 to 6 hours. By reweighing the dishes and food, the amount of each food eaten is easily obtained. By using a large number of rat.., dependable and significant results can be obtained. General deductions from the palatability teats are that raw meat, raw fish, rolled oats, JThole wheat, corn meal, bread crumbs, canned fish, canned meat, cooked cereals, cheese, meat scraps, powdered milk, fish meal, fresh vegetables, cooked vegetables, and fresh fruits rank in approximately that order. Xumerous simple and complex food mixtures showed little improvement in accept'ance over simple foods, though meat or fish and cereal mixtures were always readily eaten. The use in foods of oils of caraway, anise, catnip, cinnamon, and peppermint did not enhance palatability of the food to rats. Peppermint oil w i s repulsive to rats. I n general, the rats preferred moist to dry baits (three to one preference). However, if the baits contained added red squill powder, this preference became much less marked. I n fact rats ate three times as much dry rolled oats containing added red squill as when the mixture had been moistened. The interesting observation mas made repeatedly that rats which recovered from the effects of sublethal doses of red squill powder could rarely be induced to eat squill powder baits again, even after a lapse of several months. These same animals readily consumed baits containing alcohol or glycerol extracts of red squill. Similarly, extract baits were eaten repeatedly in sublethal doses. These facts are of great TABLE
Powder 8
PREP.4R.4TIONS
7/8
,..
700
...
Powder 4
1379
. .
... ... oi4
i;4
4/4
4/4
4;4
Oi4
... ...
...
lj4
ij4
4j4
. , .
2 j4 4/4
,..
, . .
...
7504-
950
...
...
... ... ... ...
800
... ./;
,..
... ... ...
2;z 2/2 2/2 500 -
...
+
600
significance in rat control operations because follow-up campaigns using red squill extract baits will destroy many rats which survive the effects of the original powder baits. Extracts of red squill made with ethyl or methyl alcohol or glycerol were equally palatable to rats and in every case mere much more readily eaten when mixed witJh food than when powder was used (three to one preference). Over twelve thousand returns to questionnaires sent to users of red squill baits from 1930 to 1933 are summarized by E. hl. hlills, of the I?.S. Biological Survey, in Table IV. TABLE IV. Bait Meat Fish Grain N o choice None eaten All e a t e n
BAITACCEPTANCE IN FIELD TRIALS 1930-31 1050 721 678 161 52 21
1931-32 1699 1516 1156 2405 844
1982-33 155 177 129 384 100 2 17
Total 2934 2414 1963 2953 996 235
These return> show a decided preference for meat and fish baits with+e,ereals (mainly rolled oats) in third place. I n many cwes rats are very hungry and eat all baits apparently without prefkrence. 3
%
-,
Canned R a t Baits
When the dry red squill powder was heated to 240' F. in a retort for 90 minutes, the toxicity remained unchanged. When moistened with water or mixed with such carriers as meat, fish, or cereals, and sealed in tin cans or glass iars, no CAMPAIGNS FROM SPRING, 1930, THROUGH Canned Bait, Canned Bait, 1931-193Za Fall 1933b 114 26 73,515 35,417 7,959 22.5 5,631 1,859 75 2 3,809 3,899 49.3 4,499 2,598 24
13,9i3 7,113 64 1 8.3 3,314 $115,492.86 $34.85
8,735 4,125 1,204 29.2 965 237 80 3 550 652 45.8 757 444 36.9 2,419 1,136 66 5.5 465 $16,950.25 $36.45
FALL,1933 T o t a l or Average 178 6 104,030 55,190 13.728
24.9
9,700 2,784 77.7 6,916 6,295
52.4
8,088 5,012
38.3 22,868 12,011 1,146 8.7 5,360 $180,826.27 533.92
Canned b a i t fall 1931-32 consisted of moist m e a t fish grain with powdered squill. Canned b a i t fall 1933 consisted of moist meat anb. fish' with powdered squill b u t t h e moist grain bait h a d glycerol extract of squill.
1380
INDUSTRIAL AND ENGINEERING CHEMISTRY
reduction in toxicity was noted. With this knowledge a t hand, it was possible to can successfully moist or dry readymixed red squill rat baits with no diminution in their toxicity. A preliminary report on canned rat baits was made in 1932 ( 2 ) . Further experience with canned baits has fully justified the writers’ claims for the suitability of such readymixed, preserved baits in rat eradication campaigns. They have been given extensive field trials for 3 years. Approximately three hundred thousand half-pound cans of bait were distributed to farmers and others by the U. S. Biological Survey and by state and county agricultural extension services. Some of the results of these rat campaigns are summarized in Table V, compiled by E. M. Mills, director of Rodent Control in the Northeast. These data are largely self-explanatory. The canned baits were all prepared under supervision a t a small cannery a t Barnstable, Mass. Fortyone of the campaigns were repeats. The fresh bait distributed in 1930-31 was prepared by the farmers themselves by adding 10 per cent by weight of dry red squill powder to chopped meat. There is no evidence that the toxicity of these canned baits decreased .significantly over a 2-year period of storage. Canned ready-mixed baits are easy to handle, transport, and use, are always fresh, well-mixed, and of standardized toxicity.
VOL. 27, NO. 11
They are available when needed and keep for a t least a year and probably longer. The baits consist of the foods best liked by rats, usually meat, fish, and cereals. The use of canned baits also eliminates the necessity of the user having to mix his own bait with much inconvenience and lack of equipment. The use of the canned baits has definitely met with general public approval.
Acknowledgment The writers are deeply indebted to E. M. Mills, James Silver, and J. C. Munch of the U. S. Biological Survey for many helpful suggestions and for the use of their extensive rat eradication campaign data for 1931 to 1933.
Literature Cited ( 1 ) Claremont, C. L., SnaZyst, 47, 60-7 (1922). (2) Mills, E. M., and Fellers, C. R., Canning Age,
13,200-20 (1932). (3) Munch, J. C.,Silver, J., and Horn, E. E., U. S. Dept. Agr., Tech. Bull. 134 (1929). (4) Silver, J., U. S. Dept. Agr., Farmers’BuZZ. 1533 (1927).
RECEIVED X a y 23, 1935. Presented before the Division of Agricultural and Food Chemistry a t the 89th Meeting of t h e American ChemicalSociety, New York, N. Y . , April 22 to 26, 1935.
Stimulating Employees to Invent J
HE impressive results produced by or-
JOSEPH RO S SJlAK United States Patent Office, Washington, D. C.
T
ganized research particularly during the last five years have convinced most industrial executives that a thoroughly planned research program is just as important as a good sales campaign. Many officials of large companies are realizing that better returns on the investment can be made by not confining themselves strictly to a single product or enterprise and that collateral manufacturing activities are highly desirable from the economic, social, and business viewpoints. Many large corporations are therefore manufacturing today many diverse products and are intensely interested in creating and developing new products through research. Research organized on a large scale must be carried out by employees assigned to work on specific problems. But no matter how well research departments may be conducted, the creative work must necessarily be done by individuals in the organization. The policies which such organizations follow in order t o stimulate their employees to think creatively and invent are therefore of vital importance. In order to determine the actual policies followed today, information was obtained from 233 large companies concerning the active measures they take to stimulate inventing by their employees; what incentives and rewards they offer; to what extent employees are compelled to assign their inventions in advance by contract.
Active Measure to Stimulate Inventing
READING ROOMIN THE SCIENTIFIC LIBRARY, U. S. PATENTOFFICE
It was found that eighty-nine companies took no active measures to stimulate inventing by employees, and Uty-five companies depended entirely on their engineering or research departments. Most of these companies, however, regarded promotion, increase in salary, personal prestige, and recognition as important and sufficient incentives. The attitude taken by the companies in regard to stimu1
Present address, Marathon Paper Mills Company, Rothschild, Wis.
