1888.] 



On the Vertebral Chain of Birds. 



465 



oxen. The first person who kindly called our attention to those of the 

 ox was the late Professor Pannum, of Copenhagen, who in 1874 pre- 

 sented us witfi some specimens he had found in the gall-bladder of a 

 Danish ox. 



In so far as naked eye appearances are concerned, a good specimen 

 of the variety of pearl now spoken of is quite undistinguishable from 

 a fine specimen of oriental oyster pearl, from its not only being globu- 

 lar in shape, and of a pure white colour, but from its also possessing 

 the iridescent sheen so characteristic of oriental oyster pearls of fine 

 quality. 



In chemical composition, however, mammalian pearls bear no 

 similarity whatever to pearls found in shell-fish, for they are com- 

 posed of an organic instead of an inorganic material, namely cholesterin. 

 In minute structure again, they bear a marked resemblance to the 

 crystalline variety of shell-fish pearls. 



The quantitative analysis of human pearls yielded in 100 parts — 



Water 2"05 



Solids 97'95 



The solids consisted of — 



Cholesterin 98'63 



Animal matter 1*37 



From this it is seen that human pearls are in reality nothing 

 more nor less than exceedingly pure cholesterin biliary concretions. 



This note on the chemical composition of pearls is intended as a 

 prelude to a paper we purpose shortly laying before the Society on the 

 microscopic structure of the different varieties of pearls we had the 

 honour of exhibiting sections of with the lime-light, as well as micro- 

 scopic drawings, at the soiree, on the 8th June, 1887, and of which a 

 detailed report was given in the 17th No. of the ' Cheltenham Ladies' 

 College Magazine,' pp. 37—42, by J. F. Muspratt. 



IV. "On the Vertebral Chain of Birds." By W. K. Parker, 

 F.R.S. Received March 8, 1888. 



A few years ago I noticed a remarkable fact in the development of 

 the Green Turtle (Chelone viridis), namely, that whilst thirteen 

 myotomes are developed in the cervical region, the intercalary ver- 

 tebral segments found afterwards are only eight* 



More recently, whilst working out the development of the vertebra? 

 in various types of Birds, it struck me that we have in these high 

 forms creatures in which the vertebral chain has been greatly 



* See "Challenger" Reports, Zoology, vol. 5, Plate 1, fig. 3, pp. 48 and 50. 



