Prof. Eschricht on the Gangetic Dolphin. 183 



Contrasting it with the last cervical vertebra, we now proceed 

 to the first lumbar vertebra, after which we will consider the gra- 

 dual transition of both these forms through the whole series of 

 thoracic vertebrae. In comparison with each other the two sets 

 are distinguished as usual, by the lumbar vertebrae having 

 1. the body and spinous process by far stronger; 2. the arched 

 portions seated on a level with the body of their own vertebrae ; 

 3. the processus obliqui seated on the arched portion at the origin 

 of the spinous process ; and 4. the transverse processes not only 

 increased in size equally with the spinous processes, but at the 

 same time moved down from the arched portion to the external 

 obtuse margin of the body of the vertebra itself. It is unnecessary 

 to explain further the manner in which the first point is gradu- 

 ally developed through the series of thoracic vertebrae ; it may 

 be seen in the figure (PI. V. fig. 2). As regards the altered posi- 

 tion of the arched portions, it may be accounted for by consider- 

 ing, that the gradually increasing size of the vertebrae from before 

 backwards, is greatest before, in the spinous processes ; behind, 

 in the bodies. The third and fourth points, although the deve- 

 lopment is quite as in the Dolphins generally, seem to merit 

 especial attention, on account of their having of late been con- 

 sidered as essential to the correct understanding of the vertebral 

 processes in general. 



In order to explain properly the above-mentioned third point, 

 Prof. A. Retzius* has drawn attention to the necessity of di- 

 stinguishing, as has been done already by a few older anatomists, 

 between the two parts of which the so-called processus obliqui 

 of the lumbar vertebrae may be said to be composed ; namely the 

 processus mammillares, and the real processus articulares. That 

 this distinction is well-founded is clearly shown by the Gan- 

 getic dolphin, and perhaps all other Cetacea. On looking at 

 the dorsal spine from above (PI. VII. fig. 3), the series of pro- 

 cessus mammillares is found to commence very decidedly with 

 the fifth thoracic vertebra, close to the outside of the anterior pro- 

 cessus articularis, though quite distinct from it (a) as well as from 

 the processus transversalis (/) on which the tuberculum of the 

 rib is attached (c). On the next following vertebrae, the anterior 

 articular and the mammillary processes begin to approach 

 each other more closely; the otherwise slight elevation of the 

 former process at the same time gradually disappearing, so as to 

 be seen already on the following fourth vertebra, only in the form 

 of an oblong articulating surface, seated on the inside of the 

 mammillary process itself. This structure might undoubtedly, 



* Om Ratta tydningen, &c. (On the right explanation of the lateral 

 processes of the dorsal and lumbar vertebrae in Man and Mammalia.) Trans- 

 actions of the Royal Academy of Sciences of Stockholm, 184S. 2nd part. 



