500 THE POPULAR SCIENCE MONTHLY. 



We may therefore conclude that, regarding these from the point of 

 view of nitrogenous or flesh-forming, and carbonaceous or heat-giving 

 constituents, these chief materials of flesh and of cheese are about 

 equal. 



The same is the case as regards the fat. The quantity in the car- 

 cass of oxen, calves, sheep, lambs, and pigs varies, according to Dr. 

 Edward Smith, from 16 per cent to 31"3 per cent in moderately-fatted 

 animals, while in whole-milk cheeses it varies from 21*68 per cent to 

 32*31 per cent, coming down in skim-milk cheeses as low as 6*3. Dr. 

 Smith includes Neufchdtel cheese, containing 18-74 per cent among 

 the whole-milk cheeses. He does not seem to be aware that the cheese 

 made up between straws and sold under that name is a ricotta, or crade 

 curd of skim-milk cheese. Its just value is about threepence per pound. 

 In Italy, where it forms the basis of some delicious dishes (such as 

 hudino di ricotta^ of which anon), it is sold for about twopence per 

 pound or less. 



There is a discrepancy in the published analyses of casein which 

 demands explanation here, as it is of great practical importance. 

 They generally correspond to the above of Mulder within small frac- 

 tions, as shown below in those of Scherer and Dumas : 



Scherer. Dumas, 



Carbon 54*665 53Y 



Hydrogen '7-465 7-2 



Nitrogen 15-'724 16-6 



Oxygen, sulphur 22-146 22-5 



In these the one hundred parts are made up without any phosphate of 

 lime, while, according to Lehmann ("Physiological Chemistry," vol. i, 

 p. 379, Cavendish edition), " casein that has not been treated with acids 

 contains about six per cent of phosphate of lime ; more, consequently, 

 than is contained in any of the protein compounds we have hitherto 

 considered." 



From this it appears that we may have casein with, and casein with- 

 out, this necessary constituent of food. In precipitating casein for lab- 

 oratory analysis, acids are commonly used, and thus the phosphate of 

 lime is dissolved out ; but I am unable at present to tell my readers the 

 precise extent to which this actually occurs in practical cheese-making 

 where rennet is used. What I have at present learned only indicates 

 generally that this constituent of cheese is very variable ; and I hereby 

 suggest to those chemists who are professionally concerned in the 

 analysis of food, that they may supply a valuable contribution to our 

 knowledge of this subject by simply determining the phosphate of lime 

 contained in the ash of different kinds of cheese. I would do this my- 

 self, but, having during some ten years past forsaken the laboratory 

 for the writing-table, I have neither the tools nor the leisure for such 

 work ; and, worse still, I have not that prime essential to practical re- 



