Vital Heat of Cold-blooded Animals. 155 



the same temperature as that liquid, manifesting no appre- 

 ciable vital heat. 



Mollusca and Annelides. — Berthold has shewn by experiment 

 that the Helix poniatia and slugs have a temperature inferior 

 to that of the surrounding air, and that these mollusca, when 

 plunged in water, have the same temperature as the liquid. 

 He obtained the same results with Anodonta anatina^ with 

 the medicinal leech, and earth-worms. My own experiments 

 have demonstrated that the Limax rufus^ Helix pomatia, and 

 Hirudo medicinalis, when observed in the air, are colder than 

 that medium, and that when placed in air saturated with water 

 they manifest no proper heat. 



Crustacea. — All observers, with the exception of M. Valen- 

 tin, agree in attributing no vital heat to crustaceous animals. 

 All these Crustacea possess only the temperature of the water 

 in which they live. I have been led to the same result by ex- 

 periments made on the craw-fish {Astacus flwciatilis). Neither 

 in moist air nor in water have I observed in it any vital heat . 

 The needle of the instrument was inserted into the abdomen. 

 It is well known that the Crustacea breathe by bronchiaB like 

 fishes ; the absence of appreciable vital heat in both is probably 

 owing to this mode of respiration. 



Insects. — The most extensive researches that have been 

 made on the vital heat of insects are those published by Mr 

 Newport in the Philosophical Transactions for 1837. This 

 observer employed small thermometers, one of which, usually 

 inclosed in a glass-phial, was applied to the body of the insect, 

 while another themometer, not inclosed, indicated the tempe- 

 rature of the surrounding air. Once only he introduced the 

 ball of the thermometer into the body of the cockchaffer. My 

 own researches on the subject have been made by inserting 

 the needle of the thermo-electrical apparatus into the abdomen 

 of the insect. I have in this manner obtained the exact de- 

 gree of its internal heat. Nobili and Melloni had formerly 

 appHed this instrument to ascertain the vital heat of insects, 

 but only by measuring the radiated heat that emanated from 

 their bodies. They have neither given the names of the in- 

 sects subjected to observation, nor any measurement of their 

 heat : they are satisfied with saying, " It may be admitted as 



