856 ANIMAL HEAT. 



in the blood supply alone. The difference in the temperature of the 

 two ears, after section of the cervical sympathetic on one side, may be 

 even as great as 12 or 16, but it is proportionate to the difference in 

 the quantity of blood (Schiff). If the two subclavians and the carotid 

 on the same side as the divided sympathetic are ligatured, the tempera- 

 ture of the ear falls below the normal, owing to the want of collateral 

 circulation ; on the other hand, the temperature of the ear can be raised 

 by ligature of the subclavians without section of the sympathetic nerve ; 

 this is due to the increased pressure of blood in the carotid artery 

 (Kussmaul and Tenner). The ears of a rabbit are to be looked upon as 

 part of the mechanism for regulating temperature by the varying 

 quantity of blood exposed ; section ^)f one sympathetic causes a fall in 

 the temperature of the ear of the opposite side (Jacobson and Landre). 



In addition to the vasomotor nerves of the skin, it is important to 

 remember that the vasomotor nerves to the respiratory tract and lungs 

 may play an important but subordinate part in the regulation of the 

 loss of heat. 1 The importance of this method of regulation without doubt 

 varies in different animals, and is greater in those with a thick coat of 

 fur, as in the dog, who, when he is too hot, pants with open mouth and 

 lolling tongue. This rapid respiration, 150-200 per minute in heated 

 dogs, has been specially studied by Ackerniann, 2 Goldstein, 3 and Biegel ; 4 

 more recently, Eichet 5 has shown that a dog gives off from its respiratory 

 tract, every hour, about 1 grin, of water for every kilo, of its body 

 weight, when the external temperature is moderate, but when exposed 

 to a hot sun it discharges ten times as much moisture and increases its 

 respirations from 28 to 230 per minute. Any cause which prevents a 

 clog from breathing rapidly and freely, such as a tight muzzle, causes a 

 rise of two or three degrees in the animal's temperature. 



The temperature of the body after damage or section of the 

 spinal cord. An examination of the numerous observations made upon 

 the influence of injury or section of the spinal cord shows at first sight 

 much confusion and apparent contradiction in the results. In the 

 majority of cases, however, the results can be harmonised by taking into 

 account the numerous factors of secondary import. In the first place, 

 the experiments are only strictly comparable when they are performed 

 upon similar animals under similar conditions. Thus the effect will vary 

 according to the level of the injury or section of the spinal cord ; a 

 section high up in the cord will involve a more extensive paralysis than 

 one low down, and the more extensive the paralysis the smaller the 

 production, and the greater the loss of heat, owing to the dilated cutane- 

 ous vessels. A section above the splanchnic area will obviously have a 

 greater effect than one below that area ; a section high up in the cord 

 will interfere with the movements of respiration, whereas one low down 

 will have comparatively little effect. Again, an animal with only the 

 lower extremities and part of the trunk paralysed, may be able to main- 

 tain its temperature by greater variations in the production and loss of 

 heat in the parts still under control. The size of the animal is import- 

 ant, for the bigger the animal the smaller is its surface in relation to its 



1 Bradford and Dean, Journ. PhysioL, Cambridge and London, 1894, vol. xvi. p. 34. 

 Here an account of previous work on the subject will be found. 



2 Deutsches Arch. f. Telin. Med., Leipzig, Bd. ii. S. 361. 



3 Inaug. Abhandlung, Verhandl. d. pliys. -med. Gcsellsch. in IVurzburg, 1871, S. 156. 



4 Virchoio's Archiv, 1874, Bd. Ixi. S. 396. 



5 Compt. rend. Soc. de biol., Paris, 1887, p. 482. 



