OF ORGANIC TISSUES. 127 



amount of carbon, more oxygen than the consti- 

 tuents of blood. During their formation, oxygen, 

 either from the atmosphere or from the elements 

 of water, has been added to the elements of pro- 

 teine. In hair and gelatinous membrane we ob- 

 serve, further, an excess of nitrogen and hydrogen, 

 and that in the proportions to form ammonia. 



Chemists are not yet agreed on the question, in 

 what manner the elements of sulphate of potash are 

 arranged ; it would therefore be going too far, were 

 they to pronounce arterial membrane a hydrate of 

 proteine, chondrine a hydrated oxide of proteine, 

 and hair and membranes compounds of ammonia 

 with oxides of proteine. 



The above formulae express with precision the 

 differences of composition in the chief constituents 

 of the animal body ; they shew, that for the same 

 amount of carbon the proportion of the other ele- 

 ments varies, and how much more oxygen or nitro- 

 gen one compound contains than another. 



18. By means of these formulae we can trace the 

 production of the different compounds from the 

 constituents of blood ; but the explanation of their 

 production may take two forms, and we have to 

 decide which of these comes nearest to the truth. 



For the same amount of carbon, membranes and 

 the tissues which yield gelatine contain more nitro- 

 gen, oxygen, and hydrogen than proteine. It is 

 conceivable that they are formed from albumen by 

 the addition of oxygen, of the elements of water, 



