INTRODUCTION. 31 



of readiness to contract and assume these membran- 

 ous and filmy forms peculiar to themselves, provided 

 sufficient rest be allowed for the manifestation of 

 this tendency. We can also easily recognise in the 

 blood a combination called albumen, commonly 

 found in most of the animal solids and fluids, the 

 property of which is to coagulate in boiling water. 

 In the blood are likewise discovered most of the 

 elements which can enter into the composition of the 

 animal body ; the phosphorus and lime which 

 harden the bones of vertebrated animals ; the iron 

 from which the colour of the blood itself* and of 

 various other parts is derived, and the fat, or animal 

 oil, which is deposited in the cellular membrane, and 

 serves to promote freedom and facility of motion in 

 the various parts. In fact, all the fluids and solids 



* The opinion that the colour of the blood is derived from the 

 oxide of iron, which exists in the colouring matter of this fluid, 

 was long adopted by physiologists and chemists. Dr. Wells first 

 denied the conclusion in his " Observations and Experiments on 

 the Colour of Blood," and the subsequent researches of Brande 

 and Vauquelin seem to have fully confirmed his inferences. The 

 opinion of Berzelius upon this subject, an opinion which must 

 always receive the greatest respect from physiologists, is, that the 

 colour of the blood cannot be imputed to the oxide of iron, since 

 he has no reason to conclude that this metal exists in the red 

 globules in the form of an oxide, and if it does, its quantity is in- 

 sufficient for the production cf the imputed effect. Nevertheless, 

 he conceives that iron, in its metallic state, forms one of the con- 

 stituents of these globules; these constituents are, in his opinion, 

 iron, calcium, sulphur, phosphorus, carbon, hydrogen, oxygen, 

 aud azote ; the products usually obtained by the incineration of 

 this portion of the blood are, he considers, only new combinations 

 of these elements, different from those in which they had previously 

 existed in the red globules. 



