38 Dr. P. H. Carpenter on the 



Messrs. Vogt and Yung's transverse section "frisant une syzy- 

 gie" shows the peripheral edge of one ridge and portions of two 

 others ; while two large muscular bundles are the most conspi- 

 cuous objects in the figure. The brachial nerve is not central 

 as it ought to be, and a large portion of the organic basis of the 

 arm-joint, both between it and the dorsal surface and on each 

 side of it, especially the right in the figure, has been torn away 

 by the knife, leaving a great gap which is marked " c, cavitd 

 de la syzygie." Did this cavity really exist in the position 

 figured by Vogt and Yung, it would certainly appear on the 

 dorsal side of the axial cord in a longitudinal section of an 

 arm. But on the opposite jnige of Messrs. Vogt and Yung's 

 work to that bearing the transverse section is a figure of a 

 longitudinal section in which there is absolutely no trace of 

 this cavity. There could be no better proof than this of the 

 fact that the " cavite de la syzygie " is an accidental one, the 

 position assigned to it by Vogt and Yung being within the 

 actual substance of the arm-joint. The same longitudinal 

 section on p. 559 shows two diverticula of the cadiac canal 

 towards the dorsal side with their bases resting against the 

 skeleton. One of them is lettered c, and the other with a 

 letter which is apparently meant for c, though it looks more 

 like a t ; and the explanation of the figure runs " c, c, cavites 

 de syzygies." The ^-like c, however, indicates a cavity 

 which is not at a syzygy at all, but is merely the usual diver- 

 ticulum of the coeliac canal at a muscular articulation between 

 two arm-joints. There is a similar diverticulum at every 

 syzygy, which is represented on the syzygial face by a groove 

 (see woodcut, siqrra,-p. 37, A, B) ; but it never reaches the arm- 

 nerve, as is well shown in Vogt and Yung's longitudinal section. 

 On p. 560, however, they speak of this diverticulum as en- 

 larging " vers la syzygie meme, en une cavite arrondie, plate, 

 laquelle entoure le vaisseau-nerf central, et est traversde par 

 des canaux, disposes en rayons et formes d'un tissu fibreux 

 en apparence elastique, ou musculaire, dont les insertions sur 

 les teguments donnent a des coupes bien dirigdes un aspect de 

 roue." 



As a matter of fact, however, the position of this supposed 

 " cavity de la syzygie " is not anywhere in the syzygial 

 union, but behind it, and it is occupied by the solid substance 

 of the arm-joint, as is shown in Vogt and Yung's longitudinal 

 section. 



The authors appear to have some doubt as to the real 

 nature of the fibres which effect the syzygial union ; for while 

 in the explanations of figs. 279, 280 they describe these fibres 

 as the " ligaments de la syzygie," they say on the following 



