October 7, 1910] 



SCIENCE 



453 



of the qualifications of those who offer 

 themselves for post-graduate courses. 

 There is, further, the difficulty that the 

 heads of scientific departments are not de- 

 sirous of limiting the output of new knowl- 

 edge from their laboratories by insisting on 

 the wider training for the men of science 

 who are in the process of developing as 

 students of research. 



It is perhaps true, also, that there still 

 remains a great deal unobserved or unre- 

 corded in the fields of biology, physiology 

 and biochemistry, in the investigation of 

 all of which a broad training is not 

 specially required to give good service; 

 and that, further, this condition will ob- 

 tain for one or two decades still. It is 

 quite as certain, however, that the returns 

 from such service will tend to diminish in 

 ■ number and value, and, if the coming gen- 

 eration of workers is not recruited from a 

 systematically and broadly trained class of 

 students, a period of comparative sterility 

 may supervene. 



As it is to-day, there are few who devote 

 themselves to the direct study of the chem- 

 ical and physical properties of the cell, the 

 fundamental unit of living matter. There 

 are, of course, many who are concerned 

 with the morphology of the cell, and who 

 employ in their studies the methods of 

 hardening and staining which have been 

 of verj' great service in revealing the struc- 

 tural as well as the superficial chemical 

 properties of the cell. On the facts so 

 gained views are based which deal with the 

 chemistry of the cell, and which are -more 

 or less widely accepted, but the results and 

 generalizations drawn from them give us 

 but little insight into the chemical consti- 

 tution of the cell. "We recognize in the 

 morphologists ' chromatin a substance 

 which has only in a most general way an 

 individuality, while the inclusions in the 

 nucleiis and the cytoplasm, on whose dis- 



tinction by staining great emphasis is laid, 

 can only in a most superficial way be 

 classified chemically. 



The results of digestion experiments on 

 the cell structures are also open to objec- 

 tion. The action of pepsin and hydro- 

 chloric acid must depend very largely on 

 the accessibility of the material whose char- 

 acter is to be determined. If there are 

 membranes protecting cellular elements, 

 pepsin, which is a colloid, if it diffuses at 

 all, must in some eases at least penetrate 

 them with difficulty. In Spirogyra, for ex- 

 ample, the external membrane formed of a 

 thick layer of cellulose is impermeable to 

 pepsin, but not to the acid; and, in conse- 

 quence, the changes which occur in it dur- 

 ing peptic digestion are due to the acid 

 alone. Even in the cell whose periphery 

 is not protected by a membrane, the insol- 

 uble colloid material at the surface serves 

 as a barrier to the free entrance of the 

 pepsin. It is, however, more particularly 

 in the action on the nucleus and its con- 

 tents that peptic digestion fails to give re- 

 sults which can be regarded as free from ob- 

 jection. Here is a membrane which during 

 life serves to keep out of the nucleus not 

 only all inorganic salts but also all organic 

 compounds, except chiefly those of the 

 class of nucleo-proteins. That such a mem- 

 brane may, when the organism is dead, be 

 permeable to pepsin is at least open to 

 question, and in consequence what we see 

 in the nuclel^s after the cell has been acted 

 on by pepsin and hj^di'ochloric acid can not 

 be adduced as evidence of its chemical or 

 even of its morphological character. 



The results of digestive experiments on 

 cells are, therefore, misleading. What may 

 from them appear as nucleo-protein may 

 be anything but that, while, if the pepsin 

 penetrates as readily as the acid, there 

 should be left not nucleo-protein, but pure 

 nucleic acid, which should not stain at all. 



