OF MICRO-ORGANISMS. 113 



than formerly, to show the presence of a nucleus in bacteria; but 

 that does not prove that the bacteria have none. Our knowledge 

 of the morphology of microscopic organisms is wholly relative, 

 and depends upon the degree of perfection attained by technical 

 science. When we bear in mind that the presence of a nucleus re- 

 mained for a long time unobserved in organisms several hundred 

 times larger than the bacteria, we ought not to be surprised at hav- 

 ing been unable to discover one in these smaller creatures. 



We may even go further, and question the material existence of 

 a body formed solely of protoplasm, basing our opinion upon the ex- 

 periments of Gruber, Nussbaum, and Balbiani, as reported in my 

 article, and upon the more recent observations of Klebs which are 

 in perfect agreement with the results of the investigators just cited. 

 All have shown that the nucleus is an element essential to the life 

 of the cellule, and that, when a fragment of a cellular body strip- 

 ped of a nucleus is procured by artificial section, this fragment does 

 not reproduce the organs it lost by being severed; it does not heal 

 its wound, it does not refashion its form, and, what is more, at the 

 end of a certain time its protoplasm, being withdrawn from the in- 

 fluence of the nucleus, suffers complete disorganization. These 

 experiments were made not only upon animal micro-organisms, but 

 upon vegetable cells also. They prove the primordial importance 

 of the nucleus in the cellule and thereby render doubtful the exis- 

 tence of cellules deprived of a nucleus. 



Since every cellule contains, in all likelihood, two distinct dif- 

 ferentiated elements, the protoplasm and the nucleus, which have 

 neither the same physical structure, nor the same chemical nature, 

 nor the same physiological functions, we may understand that it 

 would be exceedingly difficult to name a single instance of a 

 simple homogeneous cellule. It is the proper place to add that 

 neither protoplasm nor nucleus, each regarded by itself, are homo- 

 geneous substances. It is unnecessary to enumerate all the investi- 

 gations that have been made upon this point. Let us call to mind 

 merely the fact that from the morphological point of view proto- 

 plasm appears to be composed of two substances, a homogeneous 

 semi-liquid substance and a firmer substance exhibiting, as auth- 

 orities uppn the subject say, sometimes the form of detached fila- 

 ments and at others a structure of a reticulate character. 



At the present day, accordingly, it is impossible to allow that 

 homogeneous cellules exist, without falling back to Dujardin's 



