164 



From what I have seen of the so-called " diaphanous cor- 

 puscles" or " colloid bodies/' as well as from carefully- 

 recorded observations, I think there can be but little doubt 

 that these bodies are globules of albuminous secretion, and 

 from having seen them around a naked nucleus, and at 

 other times exuding from plasm, I think we may fairly con- 

 sider that here we have evidence again of intra-nuclear 

 secretion. 



It is by a process similar to that of secretion that nutri- 

 ment is first received into the system. It is through the 

 spongiole of the rootlet and the villus of the intestine, 

 that the highest j)lants and animals gain means of adding 

 to their tissues. In each position we find the same process 

 going on. Cells, arranged to filter and secrete, invest these 

 structures, and are from time to time renewed as they 

 become clogged and inefficient. In the spongiole the old 

 and useless cells are left to coat the rootlet as it lengthens. 

 But such an arrangement would obviously be ill-adapted to 

 alimentation in animals, and consequently the inefficient 

 cells are shed, and no elongation of the villus takes place. 

 But this first process of elaboration is not alone sufficient in 

 the higher animals ; much more remains to be done. A 

 great tubular gland, having its distal extremities stretching 

 into these villi, receives this secretion, and retains it for 

 further elaboration. This gland is furnished with free and 

 naked nuclei, which elaborate the secretion in which they 

 live, and at the same time reproduce their kind, growing and 

 dividing, by likening to themselves the surrounding fluid. 

 This is assimilation. 



These nuclei, however, though so long as they remain in 

 this gland they never invest themselves with plasm, still 

 perform the function of secretion by forming new products 

 in the surrounding liquid. Some of these nuclei pass out 

 with the fluid they have elaborated into another tubular 

 gland, and now no longer as lymph-corjDuscles, but as white 

 blood-corpuscles in a different medium, they commence a new 

 life, and form another secretion. Whether this secretion 

 invests them as it does in the lower vertebrates, or whether 

 it is detached as soon as formed, depends, perhaps, more on 

 rapidity of secretion than on the nature of the substance 

 secreted. This second secretion is the formation of the red 

 blood-corpuscle. 



I have now attempted to show that nuclear growth is the 

 true process of assimilation, and I have brought evidence to 

 show that the cell-secretion is intra-nuclear, and that many 

 tissues are mainly composed of stored secretions, histologi- 



