658 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Nerve-endings in Heart.* — A. E. Smirnow has applied both Golgi's 

 method aud Ehrlich's method to the study of the endings of the motor 

 nerves in the muscle-cells of the heart of Vertebrates. He has obtained 

 specially good results in the case of the frog's heart and those of certain 

 mammals (cat, dog, &c). He finds that each muscle-cell has its nerve- 

 ending, and that the nerve-endings are different from both the end- 

 organs of striped muscles and the plexuses of unstriped muscles. Fine 

 varicose fibrils arise from the nerve-fibres of the intra-muscular fibrillar 

 ramifications, branch repeatedly on the surface of the musclc-cclls, and 

 finally form free telodendritcs of varying form and extent in different 

 grotips of Vertebrates on the surface of the cells. 



Hair-cells of the Crista and Macula Acustica.j— Prof. ( '. M. Fiirst 

 has studied these structures, especially in salmon embryos. Each hair- 

 apparatus includes a hair (of connected cilia), a basal disc (apparently 

 composed of round corpuscles ), and a cone which is continued downwards 

 into the cell. These parts correspond to the cilia, the basal corpuscles, 

 aud the conus of a ciliated cell. The hair-apparatus, probably specialised 

 as a sensory part of the cell, has distinct structural peculiarities, but 

 the cell as a whole belongs to the ciliated type. The hypothesis of 

 Leuhossek and Henneguy, that the basal corpuscles are derived from the 

 central corpuscles, remains probable. 



Nerve End-organs in Muscle4 — Dr. Chr. Sihlcr returns to the dis- 

 cussion of some difficult points in regard to this subject. First, as to 

 the occurrence of sensory end-organs in muscles, he believes that the 

 " muscle-spindles " represent such organs. They can be readily found 

 in the muscles of snakes, lizards, and the frog, and are described in 

 detail for all three. As an example the spindle of the snake may be 

 described. It consists of three parts, the nerve, the capsule, and the 

 muscle-fibril. The last is somewhat broader than usual at the point 

 where the nerve enters, shows projections on its surface, and contains 

 a number of rounded nuclei ; at times the characteristic muscle* striping 

 is absent at the point of entrance of the nerve. The capsule consists 

 of layers of membrane, is spindle-shajied, and appears to have the same 

 composition as Henle's sheath. The nerve enters at one end of the 

 spindle and loses Henle's sheath as it enters, this being lost in the 

 capsule. It retains Schwann's sheath and the medullary sheath until 

 nearly the tip, where it rests upon the muscle. The nerve ends in a 

 plate on the surface of the muscle-fibril. As to the function of the 

 spindles, the author considers that they are probably sensitive to the 

 state of contraction of the muscle. 



A further point discussed by the author is the significance of the 

 nuclei found in the motor end-organs of muscles. He finds that these 

 nuclei, in e.g. the lizard, are of two kinds, distinguished by their shape 

 and staining reactions. He believes that the one set belongs to the 

 endothelial cells of Henle's sheath, which is continued to the end of 

 the nerve-fibrils, the other set to Schwann's sheath. He is further of 

 opinion that the end-organ lies above, and not, as has been supposed, 

 below the sarcolemma of the muscle-filu'e. 



* Anat. Anzeig., xviii. (1000) pp. 105-1") (3 figs.). 



t Tom. cit., pp. 190-203 (6 fijjs.). 



t Arch. Mikr. Anat.. lvi. (1900) pp. 331-54 (1 pi.). Cf. this Journal. 1896, p. 397. 



