496 PHYSIOLOGY CHAP. 



association of the two phenomena. In the summer, or in an 

 overheated atmosphere, the vessels dilate, and cutaneous perspira- 

 tion increases, after which the body is liable to a chill either from 

 increased irradiation of heat into the atmosphere, or by increased 

 evaporation of sweat. In the winter, or in too cold an atmo- 

 sphere, on the contrary, the skin becomes pale from vascular 

 constriction, cutaneous perspiration is diminished, and the internal 

 heat is stored up owing to the lessened dispersion at the surface 

 of the body. 



One of the earliest experiments which unmistakably shows 

 the coincidence of cutaneous hyperaemia and sweating was that 

 of Dupuy on the horse (1816), repeated and confirmed by Mayer 

 (1826), which seems to have inspired Cl. Bernard with the discovery 

 of the vaso-constrictor nerves in 1851. Division of the cervical 

 sympathetic in the horse produces a marked and persistent secre- 

 tion of sweat in the same half of the animal's head, accompanied 

 with neuro-paralytic hyperaemia. According to Mayer, galvanisa- 

 tion of the skin of the neck in man, which excites the sympathetic, 

 reduces cutaneous transpiration when it causes pallor, and increases 

 it on the contrary, both in the neck and arm, when the skin is 

 flushed. 



This correlation of the two phenomena is, however, neither 

 constant nor necessary, and countless observations and experi- 

 mental data show that the secretion of the sweat glands is directly 

 influenced by secretory nerves, which are quite independent of the 

 vasomotor innervation. The sweat, e.g. of anguish, the "cold sweat " 

 of the death-agony, and of many illnesses, particularly of con- 

 sumption, are associated with anaemia and not with hyperaemia 

 of the skin. 



In his fine researches on the vaso-dilator fibres that run in the 

 sciatic to the lower limb, Goltz (18*75) noted that excitation of 

 the peripheral end of this nerve, besides hyperaemia, determined 

 the appearance of sweat drops on the pad of the cat's foot. This 

 fact was confirmed by Kendall and Luchsinger (1876), who also 

 found that peripheral stimulation of the brachial plexus excited 

 sweat drops on the pad of the cat's front paw. They found, how- 

 ever, that this secretion is not necessarily connected with flushing 

 of the skin or increased temperature of the foot. With currents 

 that are not unduly strong the secretion of sweat can be observed 

 even when the cutaneous surface (which has no hair) becomes pale 

 and cold. They further saw that sweat can be excited on the pad 

 of the cat's foot by stimulation of the sciatic 20 minutes after 

 amputation of the limb, showing absolutely the independence of 

 the secretion from blood pressure and circulation. 



No less important were the results of Ostrumow (18*77). He 

 saw that stimulation of the abdominal sympathetic produced the 

 same effect on the cat's paw as that of the sciatic, that the effect 



