634 



PHYSIOLOGY. 



discussion of Mr. Stanley's paper in the Physical 

 Society, London, Capt. Abney said that to be 

 conclusive, the zoetrope experiments must be 

 conducted with spectrum colors instead of pig- 

 mentary ; that the statement about the size of 

 star images being less than that of a nerve ter- 

 minal would probably need revision ; and that 

 the modern view of color vision was to regard 

 light as producing chemical action in the retina, 

 which action gave rise to the sensation of color. 

 On the author's theory, he could not see how 

 color blindness could be explained. Prof. S. P. 

 Thompson said that the gist of Mr. Stanley's 

 paper seemed to be that lights of different colors 

 were concentrated at points situated at different 

 depths in the retina, the violet falling on the 

 part nearest the crystalline lens, and the red 

 farthest away. Another view of the action was 

 that the different sensations might be due to the 

 vibrations of longer wave length having to 

 travel greater distances along the nerve termi- 

 nals before they were completely absorbed. 



The aqueous humor of the eye the profuse es- 

 cape of which was formerly supposed to entail 

 the loss of the eye, but has since been ascertained 

 to be not serious in itself has been found by 

 Dr. W. Nicati, of Marseilles, to be the secretion 

 of a special glandular apparatus of the ciliary 

 process, which he calls the " uveal gland." The 

 parts described as associated with or forming 

 part of this uveal gland include an epithelium 

 continuous at the ora serrata with the retina, and 

 prolonged over the whole surface of the ciliary 

 process to the attachment of the iris. This rep- 

 resents the gland, which the author estimates to 

 have a surface at least 6 centimetres square. 

 The cells constitute a single layer, with large 

 oval or spheroidal nuclei, and rest on a layer of 

 pigment cells continuous with that external to 

 the rods and cones of the retina. Internal to 

 the epithelium is the suspensory ligament, a 

 special structure which extends from the tips of 

 the ciliary processes to the lens, and is composed 

 of delicate connective tissue and of the rigid 

 friable fibers of Henle, among which some free 

 blood corpuscles are found. These Dr. Nicati 

 believes to be the remains of the vascular organ, 

 which occupied this position before birth, the 

 tunica vascnlosa lentis, of which the pupillary 

 membrane of the foetus is a part, receiving its 

 vascular supply from the hyaloid artery. Ex- 

 ternal to the secreting epithelium is a close net- 

 work of capillaries, a continuation of the chorio- 

 capillaris, which ministers to the nutrition of 

 the ' gland. The larger arteries supplying the 

 plexus are the short ciliaries, and the veins re- 

 turning the blood are the vence vorticosce. The 

 nerves proceed from the plexus formed by the 

 ciliary nerves given off by the nasal nerve and 

 by the lachrymal ganglion. The ducts of the 

 gland are represented by the canal of Petit, the 

 circular marginal slit of the posterior chamber 

 which separates the iris in front from the crys- 

 talline lens and the ciliary processes behind, and 

 the slits connecting these spaces with each other: 

 while the channels by which the aqueous humor 

 is absorbed and carried away are lacunae in the 

 epithelial layer covering the crypts on the an- 

 terior surface of the iris, sometimes named the 

 lymphatic lacunae of Fuchs or the stomata of 

 Nuck and Cornil, which open into a system of 



lymphatic channels that are again continuous 

 with the lymphatic sheaths of the anterior and 

 posterior ciliary veins and of the vence vorticop(e. 



The results obtained by Herr Hocheisen in ex- 

 periments on the sense of touch in the blind 

 show that their muscular sense is far more acute 

 than that of those who can see, and is more 

 acute in the youthful blind than in those who 

 are older, the sense in the latter being but little 

 more acute to them in those who can see. Simi- 

 larly the power of localizing was more acute in 

 the young than in the older, and did not differ 

 appreciably from that of those who can see. I3y 

 practice both of these senses can be so sharpened 

 in those who possess sight as to become ultimate- 

 ly as acute as in the blind. Eight subjects were 

 experimented with, some of whom were born 

 blind, and some became blind early in youth. 



It appears, from the researches of Prof. 

 Zuntz, that a taste sensation, as of something 

 sweet, is increased to a very marked degree when 

 some other stimulus is simultaneously applied to 

 the organ of taste, even when the stimulus is too 

 weak to produce any sensation alone. Thus, for 

 example, a solution of sugar tastes sweeter if it 

 is mixed with some solution of common salt so 

 weak that it excites no saline taste. The same re- 

 sult was obtained by the addition of a solution 

 of quinine, also too weak to give rise of itself to 

 any sensation of taste. 



Muscular System. Physiological contrac- 

 tion, and even mere mechanical tension of the 

 flexor muscles of the knee, have been found by 

 C. S. Sherrington to exert considerable physio- 

 logical influence upon the activity of the antago- 

 nistic group of muscles, the extensors. For in- 

 stance, the elicitation of the "jerk" from the 

 extensors can be rendered difficult for a time by 

 appropriate excitation of the flexors, and can, 

 on the other hand, be much facilitated by flac- 

 cidity or paralysis of the latter. From experi- 

 ments made to determine that point it was found 

 that the tonus of extensors is heightened by ex- 

 citation of the antagonistic set, and conversely. 

 While in mutual association of action of antago- 

 nistic muscles about other joints than the knee, 

 movement in the same sense sometimes persists ; 

 the movement of response obtained is often re- 

 versed by section of the peripheral nerve or nerves 

 supplying those muscles which predominate in 

 the movement obtained, although diminished in 

 force and extent, even after cutting the nerve to 

 the predominant group of the antagonistic mus- 

 cles. This indicates that in some cases there 

 occurs, together with contraction of one group 

 of muscles, concomitant relaxation of the an- 

 tagonistic. This is more usual in the eyes than 

 in the fingers. 



Dr. Warren P. Lombard, of Clark University, 

 Massachusetts, quotes the observations of Fech- 

 ner, who spent two months in experiments on 

 the subject, on the effect of exercise upon the 

 power of endurance of the voluntary muscles. 

 This observer took note of the time required to 

 fatigue those muscles. He raised 2 dumb bells 

 of 9 pounds with extended arms over his head 

 every other second, and lowered them in the in- 

 tervening second. He found that the amount 

 of fatigue which stopped the work came on at 

 just about the same time for a considerable 

 period. The first day the exercise lasted 104 sec- 



