176 



growth; the third is chiefly produced by the influence of the exter- 

 nals to which the condition of post-foetal or independent life is 

 exposed. 



17. How far properties may communicate during all the 

 periods of foetal growth, for the purposes of that progressive causa- 

 tion which M proved by the development and conversions of the 

 structures cannot be affirmed. Properties may, during these pro- 

 cesses, assume their spheres by abstraction or separation from that 

 nucleus in which they were first combined ; or they may be identi- 

 fied in their respective spheres by subsequent communications. 

 These are relations not easily analyzed : but presuming that an in- 

 tercourse of properties does not take place without an object .or a 

 result, it may be conjectured that the communications between vital 

 properties which subserve to the establishment of functions and the 

 maintenance of independent life, either commence when the maternal 

 alliances cease, or else are preparatory to this period. The animal 

 being then exposed to the operation of new causes, these causes 

 produce other changes in his spiritual properties, which changes are 

 again influential upon connected properties. The final result of this 

 disturbance of primordial relations in the department which we are 

 considering, is to produce that blood which was before supplied by 

 the mother: this is the physical effect of the causes concerned ; and 

 the organs by which this end is accomplished are called, in reference 

 to the blood which they prepare for purposes of life, preparatory 

 organs, concerning which, respectively, some indications for inquiry 

 are now to be suggested. 



