1881.] Dr. W. Roberts. On Pancreatic Extracts. 



145 



remarkable structure only exists in the Acipenseroids ; it is not found 

 in Polyodon. 



In the Selachians the " placoid " plates or spines are not brought 

 under the influence of the chondrocranium, which has neither parosteal 

 plates applied as splints to it, nor ectosteal plates grafted upon it. 



In Acvpenser there are both parostoses applied to the oral apparatus, 

 and ectosteal centres in the post-mandibuiar arches ; moreover, along 

 the side of the skull, in old individuals, plates of bone appear as these 

 splints or parostoses, that are manifestly the forerunners of the deeper 

 plates that, in the higher Ganoids and the Teleostei, form the proper 

 ectosteal bony centres of the more or less ossified cranial box. 



The Ganoid scutes of the sturgeon are so far dominated by the 

 huge chondrocranium, that, by courtesy, they may be called frontal, 

 parietal, opercular, and the like ; of course, such scutes are not the 

 accurate homologues of the bones so named in the Teleostei, which, 

 at the most, can only correspond to the inner layer of the scute of 

 such a fish as the sturgeon. 



The sturgeons, as a group, cannot be said to lie directly between 

 any one family of the Selachians and any one family of the Bony 

 Ganoids, yet, on the whole, that is their position ; the Bony Ganoids, 

 on the whole, approach the Teleostei, especially such forms as Lepi- 

 dosteus and Amia, which have lost their "spiracle," and in other 

 things are less than typical, as Ganoids. 



Larval sturgeons are, in appearance, miniature sharks ; for a few 

 weeks they have a similar mouth, and their lips and throat are beset 

 with true teeth, that are moulted before calcification has fairly set in. 

 Their first gills are very long and exposed, but not nearly so long, or 

 for such a time uncovered, as in the embryos of sharks and skates. 



III. " On tbe Estimation of tbe Amylolytic and Proteolytic Ac- 

 tivity of Pancreatic Extracts." By William Roberts, 

 M.D., F.R.S., Physician to tbe Mancbester Royal Infirmary 

 and Professor of Clinical Medicine in Owens College. Re- 

 ceived April 23, 1881. 



The degree of activity possessed by preparations of the soluble 

 ferments cannot be ascertained by direct weighing and measuring. 

 The agents to which they owe their power have in no case been 

 obtained in a state of isolation and purity. These agents are known to 

 be indissolubly united with some form of albuminoid matter, and we are 

 constrained to speak of them as if they really were albuminoid bodies. 

 But their mode of action suggests an affinity with the imponderable 

 forces, and points to the conclusion that the relation which these 



