TROPHIC FUNCTIONS OF THE SPINA I CORD. 875 



but during the breeding season it is easily evoked. 1 There is a diurnal variation 

 of the jerk ; it is at its maximum, as a rule, soon after breakfast. 



A crossed effect is of common occurrence. It is often an adduction at 

 hip rather than an extension at knee. 2 Its time has been found much 

 longer 3 than the ordinary knee-jerk time, and sufficient to allow of its 

 being a true reflex movement ; but there are also reasons against accept- 

 ing it as such. 4 



Trophic Functions of the Spinal Cord. 



Magendie 5 showed that intracranial section of the trigeminus is 

 followed in many instances by keratitis, ulceration of lip, palate, 

 etc. Similarly, broncho-pneumonia ensues and proves fatal after 

 bilateral vagotomy. 6 Severance of the nerves of a limb produces 

 wasting not only of its muscles but of its bones and ligaments. 7 

 Section of the spermatic nerve produces atrophic changes in the 

 testis. 8 Ablation of the superior cervical ganglion leads, in the turkey- 

 cock, to atrophy of the corresponding half of the comb. 9 Section 

 of the cervical sympathetic trunk has led in young rabbits to 

 hypertrophy of the corresponding pinna, 10 although in many no 

 definite difference results. 11 Schiff 12 and S. Mayer 13 found the hair on 

 the side of the nerve-section grow the more quickly. Section of nerves of 

 the salivary glands leads to the results described in Langley's article. 14 

 The most striking of all the changes in the nutritive condition induced by 

 separation from the nerve centres is, however, that which ensues in the 

 skeletal muscles. In two or three weeks the muscle fibres begin to be- 

 come smaller, and after some months or years they have dwindled out of 

 recognition, leaving a tissue to all appearance like mere connective tissue. 



The rate of this change is very different in different muscles, 15 and in different 

 fibres of the same muscle. In the " red " muscles and " red " fibres of muscles 

 the change is slower than in the " pale." In none of the fibres of the extrinsic 

 eye muscles of the monkey did I find, sixty days after section of their nerves, 

 more than a slight increase of the interfibrillar granules that osmic acid 

 blackens ; the difference from normal was hardly discoverable. 16 The intrafusal 

 muscle fibres of the sensory organs (muscle spindles) of the skeletal muscles 

 belong to the " red " variety of fibres, and are extreme examples of that 

 variety. I am not convinced that there is any change in these muscle fibres, 

 even where the nerve to the muscle has been severed three years previously, 17 



1 Mommsen, Arch. f. Psychiat., Berlin, 1884, Bd. xv. ; and Virchoiv's Archiv, 1885, 

 Bd. ci. S. 22. 2 Hinsdale and Taylor, Internal. Med. Mag., 1895. 



3 Burckhardt, Festschr. zum Andcnkcn an Albrecht v. Hallcr, Bern, 1877 ; Gotcb, 

 Journ. Physiol., Cambridge and London, 1896, vol. xx. p. 322. 



4 PreVost and A. Waller, Rev. mid. de la Suisse rom., Geneve, 1881. 

 • r> Journ. de physiol. exper., Paris, 1824. 



6 Legallois, "Experiences sur le principe de la Vie," Paris, 1812. The literature to 

 1877 is given in 0. Prey's "Preisschrift," Leipzig, 1877. 



7 Schiff, Compt. rend. Soc. de biol., Paris, 1854, p. 1050. 



8 Obolensky, Centralbl. f. d. mcd. Wissaisch., Berlin, 1867, S. 497. 

 a Legros, " Des nerfs vasomoteurs," Paris, 1873. 



10 Bidder, Centralbl. f. Chir., Leipzig, 1874; Stirling, Journ, Anat, and Physiol., 

 London, 1876, vol. x. p. 511. 



11 C. Bernard, cited by Oilier, with Ollier's own experiments ; Oilier, Journ, de la 

 physiol. de I'homme, Paris, 1863, tome vi. p. 107; Cohnheim. " Vorlesung. ueber allgem. 

 Path.," Berlin, 1877, Bd. i. S. 599. 



12 " Untersuch. z. Physiol, d. Nervensyst.," Frankfort a/Main, 1855, S. 166. 



13 Hermann's "Handbuch," 1879, Bd. ii. Abth. 1, S. 205. 



14 This "Text-Book," vol. i. p. 519. 



15 P. Knoll, Sitzungsb. d. k. Akad. d. Wisscnsch., Wien, 1893. 



16 Journ, Physiol., Cambridge and London, 1895, vol. xv. 



17 Proc. lloy. Soc. London, 1896, vol. lx. 



