116 FOURTH REPORT 1834. 



And there enters, on the other hand, even into those organic mo- 

 tions which we call voluntary, much that is neither willed nor is 

 a matter of consciousness*. 



The following, therefore, I would signalize as the great achieve- 

 ments of modern Ph}'siology : viz. 



The establishment of the general proposition, that peculiar 

 vital powers are connected with, or inherent in, peculiar animal 

 tissues ; — dating from Haller : 



The establishment of the theory of development ; — dating from 

 G. F. Wolff: 



The further generalization which derives all the vital powers 

 from modifications of the force of Assimilation; — more fully pro- 

 pounded by Tiedemann. 



Having thus presented a rapid outline of theoretical phy- 

 siology, in which I have purposely suppressed many details 

 which may be introduced more conveniently in other parts 

 of a review of the present state of physiology, I shall now 

 proceed in that direction in which the science must for a long 

 time attempt a progressive perfection, by endeavouring to as- 

 certain, as far as is possible, the inferioi' rules by which the prox- 

 imate cause operates. These include all the processes of vege- 

 tative life ; and since they are all effected through a constant 

 interchange between external matter and the matter of the vari- 

 ous organs, I shall begin by pointing out the acquisitions added 

 in late years to our knowledge concerning the vehicle of the for- 

 mer — the blood. 



The Blood. — This fluid would be ill suited for its office, were 

 not its constituent molecules held together, in the living state, 

 by affinities so delicately balanced that they yield to every re- 

 active energy that the different organs to which it is presented, 

 can offer. Hence we account for the great discrepancies in the 

 results of chemical inquiry concerning it, from the ease with 

 which its components may be caused to combine in various pro- 

 portions, and from the different effects which different quanti- 

 ties of the same reagent are capable of producing. 



In the body it exists as a colourless transparent fluid, in which 

 an infinite number of minute red bodies are equably diffused. 



Out of the body it shortly coagulates, or separates into serum 

 and coagulum. 



It was the opinion of Home and Bauer, that the coagulum is 

 formed by an aggregation of the corpuscles in the following way. 



• Burdach, vol. iv. p. 3, &c. 



