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, we 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 “ gestaltungsfihigkeit”). 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 : 
1. An amorphous organic fluid, which in time exhibits the 
formation of— 
1. 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- 
