THE SPOUTIlSra AND MOVEMENTS OF WHALES. 635 



is inferior to the normal temperature of man. Indeed, muscular 

 or rectal temperatures liave quite indisputably given 35.4° C. for 

 Bala&noptera nmscuhis Comp. (common finback), according to Guldberg, 

 and 35.6" C. for Delphinus del])hh Cuvier (common dolphin), accord- 

 ing to Richard and Neuville, and the temperature of the liver (the 

 warmest organ of the body) 37.8° C. in Pliocsena communis (harbor 

 porpoise), according to Dav}-. Guldberg states on page 69: " We 

 may therefore regard a temperature of from 36° to 37° C. as the 

 normal temperature of the cetaceans rather than 38° to 39° C." He 

 means the temperature of the liver, which is certainly higher than 

 that of the lungs and of the air which is contained in them. 



If, therefore, the temperature of the cetaceans is sensibly inferior 

 to that of man, it is much lower than that of the majority of land 

 mammals, which have a temperature varjang around 39° C. This 

 agrees perfect!}" with what I have found for the seals and penguins 

 (Racovitza, 1900, p. 206), animals in all points comparable from a 

 physiological point of view. 



I would therefore place in opposition to the assertions of Rawitz 

 this general law: The temperature of mammals and birds modified for 

 an aquatic life, in which the bod}" is surrounded by an insulating layer 

 of fat, is inferior to the temperature of their terrestrial allies. These 

 aquatic animals do not produce more heat wherewith to counteract the 

 cold of the medium which they inhabit, but they lose less. The fat 

 which envelopes them prevents the loss of heat to such an extent that 

 a seal which has been dead for twenty-four hours and exposed to a 

 temperature of —20° C. has the viscera still warm (Racovitza, 1900, p. 

 207), and a Bataenoptera sihbaldl (sulphurbottom) three days after 

 its death gave 34° C. in the muscles and the blood (Guldberg, 1900). 



I would remark here that the fat in cetaceans, seals, and penguins 

 is not reserve matter, as in terrestrial mammals, but a veritable organ 

 of defense against cold, and I shall* support with proofs, in a memoir 

 which I have in preparation on seals and penguins, this opinion, which 

 seems a veritable paradox — that aquatic animals which have been 

 almost exterminated on account of their fat are lean animals. 



The explanation given by Rawitz is, therefore, at fault, and. further- 

 more, if it were true it would not explain why the spout of the small 

 cetaceans is not visible, since the difference between the temperature 

 of their body and the external temperature in the intertropical 

 regions would be sufficient, according to his hypothesis, to produce 

 condensation. 



My friend. Doctor Portier, chief of physiological investigations at 

 the Sorbonne, has suggested an explanation which seems to me a 

 good one. The effects of confining gases are known by w^ell-estab- 

 lished physical experiments. All gases under pressure which are 

 suddenly liberated undergo an instantaneous reduction of tempera- 



