Literary Notices. xxxi 



had occasion to criticize. But the treatment of the motor nerves, 

 which were the chief subjects of the author's own research, is masterly 

 throughout. 



Regarding the composition of the typical spinal nerves, he comes 

 to stand very nearly upon the ground of van Wijhe and Gaskell. 

 The ventral root is composed of somatic motor and visceral motor 

 fibers ; the dorsal root, of somatic sensory, visceral sensory and vis- 

 ceral motor. The latter arise from the lateral cells of Lenhossek and 

 Cajal. Now in the cranial nerves the somatic motor nerves are rep- 

 resented by the eye-muscle nerves only, while the motor roots of the 

 other cranial nerves belong exclusively to the visceral systems, their 

 nuclei being equivalent to the lateral nudei of the spinal cord. The 

 V, VII, IX and X cranial nerves therefore represent the dorsal roots 

 only of the spinal nerves and contain no somatic motor elements. 

 They are therefore homodynamous with each other, but not exactly with 

 the spinal nerves. These conclusions, to be sure, are not new; but the 

 evidence from phylogeny brought forth in support of them by Dr. Fiir- 

 bringer is of a new order and may be said to clinch the demonstration. 

 These are conclusions, moreover, to which the reviewer has m the 

 main also been led, and indeed had already formulated for the press, 

 from his own studies of the bony fishes. 



The second question propounded above is given a very thorough 

 critical treatment, but receives by no means so satisfactory an answer 

 as the first one. The reason for this is not far to seek, for neither the 

 embryology nor the adult anatomy of the critical forms has been 

 sufficiently thoroughly worked up. Dr. Fiirbringer inclines to the 

 opinion that the eye-muscle nerves are paleocranial, i. e. , that they 

 are indigenous to the head and have not migrated into it from the 

 spinal region. 



Taken as a whole this splendid research is an abundant justifica- 

 tion of its author's contention that the thorough knowledge of the 

 structure of an organ, and especially of its comparative anatomy, is 

 an essential pre-requisite for the proper interpretation of embryologi- 

 cal data concerning its ontogeny. It is a work which no writer on 

 the deeper problems of the vertebrate head can afford to ignore. 



We add a full translation of the final tables, giving the author's 

 views of the metamerism of the head. It should be noted that he 

 regards the data of the first table as far more in need of confirmation 

 than those of the second table. 



