310 A MANUAL OF VETERINARY PHYSIOLOGY 



pig, run in branches of the fifth pair of nerves. Division of the 

 cervical sympathetic in the horse produces profuse sweating 

 of the head and neck, limited to the side operated upon ; this 

 may be due to vaso-motor paralysis, though a different inter- 

 pretation has been placed on it — viz., that the sympathetic 

 carries inhibitory impulses to the sweat glands of the head, so 

 that on division the secretory fibres act without opposition. 

 In the ox Arloing has shown that division of the cervical sym- 

 pathetic causes the muzzle on the same side to become dry ; 

 stimulation of the cut end of the nerve is followed by secretion, 

 but this is not so when the nerve degenerates, though even then 

 the glands respond to pilocarpine. 



As previously stated, a high temperature favours the activity 

 of the epithelium lining the sweat glands, for if the limb of a cat 

 be kept warm, a larger secretion of sweat is obtained on stimu- 

 lating the sciatic than in a limb kept cool ; in the latter 

 stimulation of the sciatic may produce no secretion whatever. 

 Further, if a cat in which one sciatic has been divided be placed 

 in a hot chamber, profuse secretion will occur on the foot-pads 

 of the limbs not subjected to interference, while on the side on 

 which the sciatic has been divided no sweating occurs. This 

 is a further proof of the existence of a reflex mechanism, to which 

 we have already drawn attention. It has been thought that 

 the sweating which takes place at death is due to a dyspnceic 

 condition of the blood, and in many cases this may be so ; perhaps 

 it may also account for the profuse cold sweating in ruptures of 

 such viscera as the stomach and intestines ; but it cannot explain 

 the localised hot sweating which is often so well marked in horses 

 between the thighs immediately after they are destroyed. 

 Thrombosis of both iliac arteries may occur in the horse, and 

 a frequent symptom of this trouble is the peculiarity in the 

 accompanying sweating ; the general surface of the body may 

 sweat freely, but not the hind- quarters. In man a similar 

 phenomenon has been met with in cases of spinal injury. The 

 cause of this peculiarity has not been worked out. 



In comparing the sweat glands with the salivary, we must 

 be careful not to draw too close a parallel, for though in certain 

 features they agree, in others they are very different ; for 

 instance, in the horse pilocarpine produces, as in other animals, 

 a profuse salivary flow, but, unlike its action on man, the dog, 

 and cat, it has no effect whatever in producing sweating. 



The peculiar breaking out into sweats which occurs in horses 

 after work has no parallel in man ; some animals will break out 

 two and three times for hours afterwards, even after having 

 been rubbed quite dry. This may be connected with the 

 necessity for a discharge of body-heat, since the internal tern- 



