THE NERVOUS SYSTEM. 415 



again numerous fasciculi arc given off, penetrate the derma perpendicu- 

 larly, and, having reached the superficial glandular layer of the skin, 

 form a superficial nervous-plexus between the glands. "With respect to 

 the true termination of the nerve-fibres, Czerraiik arrived at no definite 

 results, but made the interesting discovery that thick and thin nerve- 

 fibres of the deeper plexus divide dichotomously very frequently and 

 repeatedly, and thus spread themselves over larger surfaces; of Avhich 

 divisions I have most fully satisfied myself from preparations furnished 

 by Czermtik. Similar conditions were found by Leydig (" Zeitsch. f. 

 wissen. ZooL," III.) in the skin of Fishes; where also exist superficial 

 and deeper plexuses, with numerous divisions of finer and thicker tubes, 

 all of which on the surface ultimately become quite fine, pale, and finally 

 invisible. In the Invertebrata, as appears from Leydig's researches in 

 Argulus, and especially in Carinaria, conditions are met with perfectly 

 analogous to those described by me in the nerves of the Tadpole ; and I 

 cannot agree with Leydig, when he describes the nucleated enlarge- 

 ments as nerve-cells. On the other hand, the conditions observed in 

 Arteviia and Corcthra are perhaps, peculiar, because in these instances 

 larger branches of the cutaneous nerves are, at their extremities, in con- 

 nection with numerous roundish vesicles, which might have the function 

 of nerve-cells (" Zeitsch. f. wiss. Zool.," vol. I. iii.). 



In the integuments of the Mammalia and of Man, except in the Paci- 

 nian bodies, until a short time since, no one had seen anything of divi- 

 sions in the nerve-tubes ; all observers rather agreeing that terminal 

 loops existed there, especially in the papillse. But it now appears, from 

 the researches of myself, J. N. Czermak, and C. Gegenbaur, that pro- 

 bably loops and divisions, and occasionally even free terminations, all 

 exist in that situation. That in Man, terminal loops occur in the 

 papillae, and divisions in the terminal plexuses, I have already men- 

 tioned ; the latter are especially well shown in the conjunctiva scleroticce, 

 where free terminations also appear to exist, and where peculiar convo- 

 lutions of nerves (nerven-knauel), similar to those formerly described by 

 Gerber* [vide " Micr. Anat.," II. i. p. 31, Fig. 13 A, 3), present them- 

 selves. Czermdk, moreover, observed divisions of the cutaneous nerves 

 in the Mouse, and I myself a transition of the dark-bordered nerves into 

 pale anastomosing filaments, of O-OOl-O'OOOo of a line, exactly resem- 

 bling the embryonic fibres in the Tadpole (" Micr. Anat.," II. i. p. 24) ; 

 lastly, Gegenbaur has noticed numerous divisions in the expansion of the 

 nerves of the tactile hairs in the Mammalia. Further experience will 

 have to show in what relative proportions the loops, divisions, and free 

 terminations, stand with respect to each other, and whether in the diffe- 

 rent Mammalia, notwithstanding any apparent difference, some corre- 

 spondence obtains or not. 



* ["General Anatomy," translated by G. Gulliver, p. 263, pi. 19, Figs. 99, 100.— Trs.] 



