238 DR. ORD. 



A table, to be found at page 20 in vol. i of Owen's ' Ana- 

 tomy of Vertebrates/ being taken as a guide, solutions were 

 arranged to give by mutual decomposition the following pro- 

 portions : 



G4;"4! phosphate, 7'03 carbonate of calcium, as ia hawk, 

 59*6 „ 7"3 „ „ „ man. 



52'6 „ 12"53 ,j ,, „ tortoise. 



57-3 „ 4-9 „ „ „ cod. 



The first tAvo were placed in hot beds of different tempera- 

 tures, the hawk quantities in the warmer ; the others were 

 left in a cool room, so that the temperatures of about 85°, 

 75°, and 60° Fahr., were severally obtained. It followed 

 that, in warmth or in cold, phosphate of lime was evenly dis- 

 tributed through the albumen in definite strata, not forming 

 crystals or spheres, but cementing the albumen to great hard- 

 ness, particularly at the line of greatest density. Carbonate 

 of lime, on the other hand, never failed to form spheres at 

 the highest temperatures used. At the lower temperatures, 

 however, it took very remarkable forms. In certain strata 

 were found spheres of very regular size, having a much smaller 

 diameter than the sjjheres formed at ordinary temperatures, 

 and these spheres were closely beset with transparent often 

 curved and pointed spines, so that the whole structure came 

 to resemble the spiny spores of some of the Desmidiee. These 

 spines were evidently attempts at crystallisation, which, as 

 before noted, is favoured by cold, and which would be able 

 to assert itself Avhen the spheres had attained a certain bulk, 

 and radial attraction had thereby been sufficiently enfeebled. 

 Indeed, in some cases they were so arranged as to form a 

 sketch of rhombohedron investing the central sphere. 



In the bone-salt experiments a nearly uniform result was 

 obtained throughout. The carbonate of lime was subdued, 

 so to speak, by the phosphate, and an even subcrystalline but 

 continuous deposit was produced. "With transmitted or re- 

 flected light no spheres could be seen, but with polarized 

 light indications of their existence were in some parts mani- 

 fested by crosses of faint white and black. The use of a 

 phosphate as a cement and manipulator of the less tractable 

 carbonate is well indicated in these experiments. 



The strength of the carbonate seems necessary in all hard 

 tissues that have to be tough. But the carbonate alone does 

 not appear to be fitted to form tissue destined to be the seat 

 of active interstitial change. With the bird's high temjjera- 

 ture and great vital activity, therefore, we see associated a 

 great predominance of phosphate. In the tortoise, with its 

 low temperature and sluggish processes, a great decrease of 



