450 



re-actions of elements differing in physical and chemical cha- 

 racters, are in full operation. 



From the foregoing observations, and especially from the 

 results of researches in Histolysis, I am induced to believe that 

 in the formation of organic structures we may detect two 

 quite distinct modes of growth and development, the one phy- 

 sical, the other organic (properly so called) or vital, the former 

 taking place in obedience to certain physical laws alone ; the 

 latter, though operating by physical laws, yet guided and di- 

 rected by a force which, for the want of a better name, Ave are 

 compelled to call vital. 



The elements which result from these modes of growth 

 differ widely in function and destination (the latter alone pos- 

 sessing the " gestaltungsfahigkeit"). There is reason, I think, 

 to believe that the primary phases of Histogenesis are in a con- 

 siderable measure similar to some of the artificial processes 

 which have been above alluded to, and that in the history of 

 development the following is the order of appearance of the 

 elementary parts : 



i. An amorphous organic fluid, which in time exhibits the 



formation of — 

 II. Primary organic granules, granular corpuscles, granu- 

 lar base or stroma, hyaline membrane, hyaline base 

 or stroma, and hyaline vesicles. 

 Here we have an assemblage of elements of a simple kind which 

 are to be met with, some or all variously combined in the ex- 

 amination of animal tissues and fluids : they are, in fact, the 

 rubble work of the organic edifice, but have themselves no 

 share in determining its development, being a-plastic, or inca- 

 pable of generating higher tissues, though they may serve as 

 pabulum for the more active plastic elements. But in the 

 living organism we have elements of a still higher order, pos- 

 sessed of wonderful vitality, which we may suppose to be of 

 later origin, and of whose mode of genesis we have still but 

 very imperfect conceptions. These elements I will denomi- 



