582 TROPHIC NERVES AND TROPHONEUROSES. 



cervical sympathetic nerve in young, growing animals is followed by a more rapid growth of the 

 ear uj>on that side {Bidder, Stirling, Strieker), also of the hair on that side {Schiff, Stirling) ; 

 while it is said that the corresponding half of the brain is smaller, which, perhaps, is due to 

 the pressure from the dilated blood-vessels (Broicn-Sequard). 



Blood- Vessels. Lewaschew found that prolonged uninterrupted stimulation of the sciatic 

 nerve of dogs, bv means of chemical stimuli [threads dipped in sulphuric acid], caused hyper- 

 trophy of the lower limb and foot, together with the formation of aneurismal dilatations upon 

 the blood-vessels. 



Skin and Cutaneous Appendages. In man, stimulation or paralysis of nerves, or degeneration 

 of the grey matter of the spinal cord, is not unfrequently followed by changes in the pigmenta- 

 tion of the skin, in the nails, in the hair and its mode of growth and colour (Jarisch). [Injury 

 to the brain, as by a fall, sometimes results in paralysis of the hair follicles, so that, after such 

 an injury, the hair is lost over nearly the whole of the body.] Sometimes there may be erup- 

 tions upon the skin, apparently traumatic in their origin (v. Barcnsprung). Sometimes there is 

 a tendency to decubitus ( 379), and in some rare cases of tabes, there is a peculiar degeneration 

 of the joints (Charcot's disease). The changes which take place in a nerve separated from its 

 centre are described in 325. 



[Trophoneuroses. Some of the chief data on which the existence of trophic nerves is assumed 

 are indicated above. There are many pathological conditions referable to diseases or injuries of 

 nerves.] 



[Muscles. As is well known, paralysis of a motor nerve leads to simple atrophy of the 

 corresponding muscle, provided it be not exercised ; but when the motor ganglionic cells of the 

 anterior horn of grey matter, or the corresponding cells in the crus, pons, and medulla, are 

 paralysed, there is an active condition of atrophy with proliferation of the muscular nuclei. 

 Progressive muscular atrophy, or wasting palsy, is another trophic change in muscle, whereby 

 either individual muscles, or groups of muscles, are one after the other paralysed and become 

 atrophied. In pseudo-hypertrophic paralysis, there is cirrhosis or increased development of 

 the connective-tissue, with a diminution of the true muscular elements, so that although the 

 muscles increase in bulk their power is diminished.] 



Cutaneous Trophic Affections. Amongst these may be mentioned the occurrence of red 

 patches or erythema, urticaria or nettle-rash, some forms of lichen, eczema, the bulla} or blebs 

 of pemphigus, and some forms of ichthyosis, each of which may occur in limited areas after 

 injury to a nerve or its spinal or cerebral centre. The relation between the cutaneous eruption 

 and the distribution of a nerve is sometimes very marked in herpes zoster, which frequently 

 follows the distribution of the intercostal and supraorbital nerves. Glossy skin (Paget, Weir 

 Mitchell) is a condition depending upon impaired nutrition and circulation, and due to injuries 

 of nerves. The skin is smooth and glossy in the area of distribution of certain nerves, while 

 the wrinkles and folds have disappeared. In myxcedema, the subcutaneous tissue and other 

 organs are infiltrated with, while the blood contains, mucin. The subcutaneous tissue is 

 swollen, and the patient looks as if suffering from renal dropsy. There is marked alteration 

 of the cerebral faculties, and a condition resembling a "cretinoid state" occurs after the 

 excision of the thyroid gland. Victor Horsley has shown that a similar condition occurs in 

 monkeys after excision of the thyroid gland ( 103, III.). [Laycock described a condition of 

 nervous oedema which occurs in some cases of hemiplegia, and apparently it is independent of 

 renal or cardiac disease.] 



[There are alterations in the colour of the skin depending on nervous affections, including 

 localised leucoderma, where circumscribed patches of the skin are devoid of pigment. The 

 pigmentation of the skin in Addison's disease or bronzed skin, which occurs in some cases of 

 disease of the suprarenal capsules, may be partly nervous in its origin, more especially when we 

 consider the remarkable pigmentation that occurs around the nipple and some other parts of 

 the body during pregnancy, and in some uterine and ovarian affections. 



In anaesthetic leprosy, the anaesthesia is due to the disease of the nervous structure, which 

 results in disturbance of motion and nutrition. Amongst other remarkable changes in the 

 skin, perhaps due to trophic conditions, are those of symmetrical and local gangrene, and 

 acute decubitus or bed-sores.] 



[Bed-Sores. Besides the simple chronic form, which results from over-pressure, bad nursing, 

 and inattention to cleanliness, combined with some defect of the nervous conditions, there is 

 another form, acute decubitus, which is due directly to nerve influence (Charcot). The latter 

 usually appears within a few hours or days of the cerebral or spinal lesion, and the whole cycle 

 of changes from the appearance of the erythematous dusky patch to inflammation, ulceration, 

 and gangrene of the buttock is completed in a few days. An acute bed-sore may form 

 when every attention is paid to the avoidance of pressure and other unfavourable conditions. 

 When it depends on cerebral affections, it begins and develops rapidly in the centre of the 

 gluteal region on the paralysed side, but when it is due to disease of the spinal cord, it forms 

 more in the middle line in the sacral region ; while in unilateral spinal lesions it occurs not on 

 the paralysed, but on the anesthetic side, a fact which seems to show that the trophic, like the 

 sensory fibres, decussate in the cord (Ross) 1 



