8s 6 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 (Schifi). 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 of 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 Aekermann,- Goldstein, 3 and Eiegel; 4 
more recently, Richet 5 has shown that a dog gives off from its respiratory 
tract, every hour, about 1 grm. 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 
dog 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, Jonm. Physiol., Cambridge and London, 1894, vol. xvi. p. 34. 
Here an account of previous work on the subject will be found. 
3 Deutsche* Arch. f. Jclin. Med., Leipzig, Bd. ii. S. 361. 
3 Inaug. Abhaudlung, Verhamdl. d. phys.-med. Gcsdlsch. in Wurzburg, 1S71, S. 156. 
4 Virchow's Archiv, 1874, Bd. lxi. S. 396. 
5 Compt. rend. Soc. dc biol., Paris, 1887, p. 482. 
