106 The American’ Naturalist. [February, 
in nuclei as well as in cells poor in nuclear elements. We 
must reiterate, however, that the first place in importance 
among these so-called primary bodies is to be ascribed to the 
proteids in all living cells, for it seems more than probable 
that the nucleins and the lecithins found in cell protoplasm 
are constructed synthetically out of certain cleavage products 
of the proteids and phosphates. However this may be, the 
globulins, nucleo-albumins and nucleins are, so far as our 
present knowledge extends, the important constituents of cell 
protoplasm in all animal and vegetable cells. Of these three 
classes of bodies, the nucleins and the related nucleo-albumins 
are deserving of special notice. 
The substance originally known as nuclein and first identi- 
fied by Hoppe-Seyler and Miescher as the main constituent 
of the nucleus of pus cells was prepared by a number of in- 
vestigators from different kinds of material rich in nuclei, or 
nuclear substance. Thus, Miescher prepared it from the sper- 
matozoa of different animals, Geoghegan from the. brain, 
Hoppe-Seyler from yeast cells, Plész from the liver and von 
Jaksch from the human brain. The products obtained, how- 
ever, while showing certain points in common, were unlike 
each other in many respects. Thus, they were all alike in 
containing a noticeable amount of phosphorus, but the per- 
centage of phosphorus was found on analysis to vary from 1.8 
per cent. up to 9.5 per cent. Again, the several products dif- 
fered in their degree of solubility in alkalies, some being very 
soluble and others only slightly so. These marked discrepan- 
cles were naturally considered as implying that the so-called 
nuclein was not a chemical unit, but rather an indefinite mix- 
ture of organic phosphorus compounds with proteid matter: 
but we now know, thanks to the painstaking work of Kossel 
and others, that there are a group of closely related bodies, 
nucleins, widely distributed in nature, wherever cell structuré 
” to be found, as the main constituent of the cell nucleus, and 
likewise present in certain substances such as milk and egg- 
yolk which serve as food for developing animals. The latter 
class are better known as nucleo-albumins, from which & 
typical nuclein can be separated or rather prepared by the 
