Among poikilothermal vertebrates and invertebrates, there are many useful materials for pharmacological research including the primary screening of drugs.
In our country, some species have been used in the fields of pharmacy and medicine, frog and toad are rather popular for the screening of cardiotonics, less commonly killifish for the pharmacological research of digitalis, crab for the assay of gamma-aminobutyric acid. However, generally speaking, many of those are less familiar to pharmacologists or medical scientists than to zoologists. As those lower animals are rather remote from human beings, and no systematic work has been done to utilize them as experimental animals. Besides, the majority of those animals used currently have been given no consideration for selecting, breeding, and for care. So, it is necessary to enlighten the usefulness of those animals for research and bioassay.
Following items are included in this article.
1) General features of poikilothermal vertebrates and invertebrates.
2) Species widely used for scientific research in Japan.
3) Some hints on the usefulness for experimental purpose of organs from poikilothermal animals.
4) Problems in the utilization of lower animals.
5) New and old literature, mainly with respect to the effect of drugs.

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Natural hemagglutinins against chick erythrocytes in mouse sera were studied with several inbred strains established in Japan. When the chick erythrocytes of Nagoya breed (line B) were used for hemagglutination test, the percentage of animals possessing the agglutinins was as follows; CS: 18.5, NC: 44.2, KK: 45.9, DDK: 50.7, CF#1: 42.1, C57BL/6: 58.3.
It was found that the agglutinating capacity of the mouse sera differs markedly according to cells used. The mouse sera which failed to agglutinate the cells from the Nagoya breed, showed strong positive reaction with the cells from the Jito groups of chicken.
Reciprocal absorption tests revealed that there are at least two qualitatively different agglutinins in mouse sera. It may be suggested that the hemagglutination caused by mouse sera could be a useful tool for the classification of chick erythrocyte groups.

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Seventy-two Wistar strain male rats, weighing 150-180g, were used. The change of the body temperature of the rats placed outdoor was measured, and the lethal temperature of them was obtained.
The results obtained were as follows:
1) At the atmospheric temperature of 30-35°C under the direct sun beam, all of the animals died, and average lethal body temperature of the rats was 44°C.
2) At 29-33°C of atmospheric temperature, even under the direct beam, 4 rats out of 14 have survived.
3) The distribution of the lethal body temperature of rats after the exposure to the direct sunshine was as follows:
43.6-44.0°C 33.3%
43.1-43.0 25.0
42.6-43.0 25.0
42.1-42.5 12.5
41.5-41.6 4.2
4) When shaded, all the rats survived and their diurnal body temperature never exceeded 38.8°C.

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