Literary Notices. xxvii 



that in the conflict, above referred to, between the somatic metameres, 

 which push forward, and the branchiomeres, which push backward, 

 the motor spinal nuclei migrate cephalad under the motor vagus 

 nucleus, while the corresponding sensory spinal nuclei are checked in 

 their migration by the sensory vagus nuclei and hence degenerate, 

 their peripheral areas being supplied by the vagus. 



To this principle we assent, but in its application in the present 

 instance it seems to us that Dr. Fiirbringer has perpetuated an ancient 

 and very pernicious morphological error. That is, he regards the 

 sensory rami of the spinal nerves and the ramus lateralis of the vagus 

 as equivalent structures, while the fact is that recent research has 

 abundantly shown that these nerves belong to entirely distinct cate- 

 gories of sensory nerves, having no relation to each other either cen- 

 trally or peripherally, and to regard them as equivalent or capable of 

 replacing each other is bad morphology, as well as bad physiology. 

 General cutaneous nerves, such as the dorsal rami of the spinal 

 nerves, cannot be either functionally or morphologically replaced by 

 special cutaneous nerves, such as the rami laterales of the X and IX 

 nerves, which belong to the acustico-lateral system. Nor is such an 

 unnatural substitution necessary, for we know that in the other Ich- 

 thyopsida, and presumably in the Selachii, the vagus contains other 

 fibers which do belong to the general cutaneous component. These 

 are derived from the spinal V tract and are distributed with the su- 

 pratemporal rami of X and IX. They may accompany lateralis fibers 

 but can be distinguished from them. A survey of the existing litera- 

 ture leaves no doubt in the mind of the reviewer that similar relations 

 will be found to prevail in the selachians. It is therefore the rami 

 cutanei dorsales of the X and IX nerves and not their rami laterales 

 that have replaced the dorsal rami of the spino-occipital. 



Again in the final comparison between the true cranial and the 

 spinal nerves (p. 570), Dr. Fiirbringer states that with reference to 

 the homology (in the broad view) of the sensory roots of the cranial 

 and spinal nerves there is scarcely any controversy. This is a very 

 rash statement in view of the recent work on the components of the 

 cranial nerves (Pollard, Strong, Cole, Kingsbury, Herrick), for the 

 evidence is rapidly accumulating that the special cutaneous compo- 

 nents (acustico-lateral and communis systems) are neomorphs in the 

 head and that the general cutaneous (spinal V) system is the only 

 representative in the head of the cutaneous nerves of the trunk. 



The principle involved in this criticism has a profound and far- 

 reaching application. The comparisons instituted in some of our 



