448 PATHOLOGICAL VARIATIONS. 



Anterior Extremity. The secretory fibres lie in the ulnar and median nerves, 

 for the fore-limbs of the cat ; most of them, or indeed all of them (Nawrocki), pass 

 into the thoracic sympathetic (GgL stellatum), and part (?) run in the nerve-roots 

 direct from the spinal cord (Luchsinger, Vulpian, Ott). A similar sweat-centre 

 for the upper limbs lies in the lower part of the cervical spinal cord. Stimulation 

 of the central ends of the brachial plexus causes a reflex secretion of sweat upon 

 the foot of the other side (Adamkiewicz). At the same time the hind feet also 

 perspire. 



Pathological. Degeneration of the motor ganglia of the anterior horns of the spinal cord 

 causes loss of the secretion of sweat, in addition to paralysis of the voluntary muscles of the 

 trunk. The perspiration is increased in paralysed as well as in oedematous limbs. In nephritis, 

 there are great variations in the amount of water given off by the skin. 



Head. The secretory fibres for this part (horse, man, snout of pig) lie in the 

 thoracic sympathetic, pass into the ganglion stellatum, and ascend in the cervical 

 sympathetic. Percutaneous electrical stimulation of the cervical sympathetic in 

 man, causes sweating of that side of the face and of the arm (M. Meyer). In the 

 cephalic portion of the sympathetic, some of the fibres pass into, or become applied 

 to, the branches of the trigeminus, which explains why stimulation of the infra- 

 orbital nerve causes secretion of sweat. Some fibres, however, arise directly from 

 the roots of the trigeminus (Luclisinger), and the facial (Vidpian, Adamkieiuicz). 

 Undoubtedly the cerebrum has a direct effect either upon the vaso-motor nerves 

 (p. 447, I.) or upon the sweat-secretory fibres (II.), as in the sweating produced by 

 psychical excitement (pain, fear, &c). 



Adamkiewicz and Senator found that, in a man suffering from abscess of the motor region of 

 the cortex cerebri for the arm, there were spasms and perspiration in the arm. 



Sweat-Centre. According to Adamkiewicz, the medulla oblongata contains the 

 dominating sweat-centre ( 373). When this centre is stimulated in a cat, all 

 the four feet sweat, even three-quarters of an hour after death (Adamkiewicz). 



III. The nerve-fibres which terminate in the smooth muscular fibres of the sweat- 

 glands act upon the excretion of the secretion. 



[Changes in the Cells during Secretion. In the resting glands of the horse, the cylindrical 

 cells are clear with the nucleus near their attached ends, but after free perspiration they become 

 granular, and their nucleus is more central (Eenaut).] 



If the sweat-nerves be divided (cat), injection of pilocarpin causes a secretion of sweat, even 

 at the end of three days. After a longer period than six days, there may be no secretion at all. 

 This observation coincides with the phenomenon of dryness of the skin in paralysed limbs. 

 Dieffenbach found that transplanted portions of skin first began to sweat when their sensibility 

 was restored. If a motor nerve (tibial, median, facial) of a man be stimulated, sweat appears 

 on the skin over the muscular area supplied by the nerve, and also upon the corresponding area 

 of the opposite non-stimulated side of the body. This result occurs when the circulation is 

 arrested as well as when it is active. Sensory and thermal stimulation of the skin always cause 

 a bilateral reflex secretion independently of the circulation. The area of sweating is inde- 

 pendent of the part of the skin stimulated. 



288. PATHOLOGICAL VARIATIONS. 1. Anidrosis or diminution of the secretion of 

 sweat occurs in diabetes and the cancerous cachexia, and along with other disturbances of 

 nutrition of the skin in some nervous diseases, e.g., in dementia paralytica ; in some limited 

 regions of the skin, it has occurred in certain tropho-neuroses, e.g., in unilateral atrophy of the 

 face and in paralysed parts. In many of these cases it depends upon paralysis of the corre- 

 sponding nerves or their spinal sweat-centres. 



2. Hyperidrosi8, or increase of the secretion of sweat, occurs in easily excitable persons, in 

 consequence of the irritation of the nerves concerned ( 288), e.g., the sweating which occurs in 

 debilitated conditions and in the hysterical (sometimes on the head and hands), and the so- 

 called enileptoid sweats {Eulcnburg). Sometimes the increase is confined to one side of the head 

 (H. unilateralis). This condition is often accompanied with other nervous phenomena, partly 

 with the symptoms of paralysis of the cervical sympathetic (redness of the face, narrow pupil), 

 partly with symptoms of stimulation of the sympathetic (dilated pupil, exophthalmos). It may 

 occur without these phenomena, and is due perhaps to stimulation of the proper secretory fibres 

 alone. [Increased sweating is very marked in certain fevers, both during their course and at 

 the crisis in some ; while the sweat is not only copious but acid in acute rheumatism. The 

 " night-sweats " of phthisis are very marked and disagreeable.] 



