TROPHIC CENTRES AND NERVES. 741 



fact in the most conclusive manner. He divided the fourth, fifth, sixth, seventh, and 

 eighth pairs of lumbar nerves on one side in a dog, at the spinal column, and paralyzed 

 motion and sensation in the leg of that side, but the temperature of the two sides remained 

 the same. He afterward exposed and divided the sciatic nerve on that side, and then 

 noted a decided increase of temperature. This experiment, which is only one of a large 

 number, shows conclusively that the ordinary mixed nerves contain vaso-motor fibres, 

 which are entirely independent of the nerves of motion and sensation, a fact which is 

 admitted by all physiologists and has frequently been illustrated in cases of disease in the 

 human subject. 



It only remains to show that the phenomena following section of the sympathetic in 

 animals are illustrated in certain cases of disease or injury in the human subject. It is 

 excessively rare to observe traumatic injury confined to the sympathetic in the neck. A 

 single case, however, apparently of this kind, has lately been reported by Mitchell. A 

 man received a gunshot-wound in the neck. Among the phenomena observed a few- 

 weeks after, were, contraction of the pupil on the side of the injury, and, after exercise, 

 flushing of the face upon that side. There was no difference in the temperature upon 

 the two sides, during repose, but no thermometric observations were made when half of 

 the face was flushed by exercise. Dr. Bartholow has reported several cases of unilateral 

 sweating of the head (two observed by himself), in several of which there was probably 

 compression of the sympathetic from aneurism. In those cases in which the condition 

 of the eye was observed, the pupil was found contracted in some and dilated in others. 

 In none of these cases were there any accurate thermometric observations. In a series 

 of observations by Wagner, upon the head of a woman, eighteen minutes after decapita- 

 tion, powerful galvanization of the sympathetic produced great enlargement of the pupil. 

 In such a case as this, it would not be possible to make any observations on the influence 

 of the sympathetic upon the temperature. 



Trophic Centres and Nerves (so called). 



We have deferred the consideration of the so-called trophic nerves until we had 

 treated of the functions of the sympathetic system, because the vaso-motor nerves, by 

 their influence upon the circulation, are evidently connected with the phenomena of 

 nutrition. It is not necessary to dwell very minutely upon this point; but cases of 

 disease, as well as experiments upon the inferior animals, show that, when a muscle is 

 paralyzed, as a result of the abolition of nervous influence and consequent disease, it 

 becomes atrophied, its fibres lose their characteristic structure and finally become inca- 

 pable of contracting under a stimulus. As we have seen that the cerebro-spinal 

 nerves, in addition to their motor and sensory fibres, contain vaso-motor elements, it 

 becomes a question whether the muscles be supplied with special nerves aside from those 

 of motion and sensation and the vaso-motor nerves which preside over their nutrition. 

 Such could properly be called trophic nerves. Many pathologist*, relying upon the 

 presence of certain lesions of cells in the cord, in connection with cases of progressive 

 muscular atrophy, admit the existence of trophic cells and nerves. It must be admitted, 

 however, that these views rest upon pathological facts alone and have not been demon- 

 strated by physiological experiments or observations. 



After what we have said, it is evident that proper nutrition of the muscular system 

 depends upon its exercise and the integrity of its motor nerves. In the second place, the 

 history of monsters shows that the muscular system may be developed independently of 

 the cerebro-spinal centres. In the admirable work of Brachet, upon the gamrlionir s\>.trm, 

 numerous cases of anencephalic monsters are detailed, in which the muscular system was 

 found more or less perfectly developed. In some of these, the f.i-tus was delivered at 

 term and lived for several hours. When we consider the great number of cases of this 

 kind on record, a few of which only are cited by Brachet, it is evident that the cerebro- 



