366 THE MICBOSCOPE. 



from the food to the blood-vessels, for the reparation of the framework 

 or growth that so incessantly goes on in the animal body. In Plate 

 XII. No. 3 6 is shown the arrangement of the chyliferous tubes, with 

 their corpuscles enclosed in a structureless membrane. 



And thus we shall find that all the tissues most actively engaged 

 in the maintenance of the vital functions of the human body are per- 

 formed by these cells or globules, varying in size from infinite mi- 

 nuteness to forms visible to the unassisted eye ; that one system 

 of cells secretes the bile, another the fat, another the nerve-matter, 

 and so forth. But how these special products are formed by cells 

 apparently of similar organisation, we know not. Whether the 

 special endowment belonging to the system of cells of a particular 

 organ depends on the intimate structure of the wall or tissue of such 

 cell^, and this structure be so attenuated and infinitesimal as to 

 elude our observation, or whether it results from the transmission 

 of some peculiar modification of that mysterious vital force we term 

 nervous influence, are questions to which no satisfactory reply can be 

 given. 



Mr. Huxley has ascertained, that in all the animal tissues the so- 

 called nucleus (endoplast) is the homologue of the primordial utricle, 

 with nucleus and contents (endoplast) of the plant, the other histo- 

 logical elements being invariably modifications of the periplastic 

 substance. Upon this view, we find that all the discrepancies which 

 had appeared to exist between the animal and vegetable structure dis- 

 appear ; and it becomes easy to trace the absolute identity of plan 

 in the two, the differences between them being produced merely 

 by the nature and form of the deposits in, or modifications of, the 

 periplastic substance. In both plants and animals there is but one 

 histological element — the endoplast — -which does nothing but grow 

 and vegetatively repeat itself; the other element — the periplastic 

 substance — ^being the subject of all the chemical and morphological 

 metamorphoses in consequence of which specific tissues arise. The 

 differences between the two kingdoms are mainly, firstly. That in the 

 plant the endoplast grows, and, as the primordial utricle, attains a large 

 comparative size, while in the animal the endoplast remains small, the 

 priiicipal bulk of its tissues being formed by the periplastic substance ; 

 and secondly. In the nature of the chemical changes which take place 

 in the periplastic substance in each case. 



