J36 LIFE : OUTLINES OF GENERAL BIOLOGY 



with correct results; sixty-three towls were correctly diagnosed out 

 of seventy-seven. 



Sometimes the aid that chemistry gives is of the nature of a 

 technical method; thus the elegant Japanese instrument called a 

 biometer. which measures very minute quantities of carbon dioxide, 

 is used in estimating the intensity of metabolism at different parts 

 of an animal, and has helped towards the establishment of the 

 profoundly important biological idea of metabolic gradients of 

 intensity. Thus we know that in a simple worm the intensity of 

 the vital processes wanes from the head and backwards for a certain 

 distance. Here we should take cognisance of the marvellously exact 

 methods of micro-analysis devised by Prof. Pregl of Graz, a 

 Nobel prizeman, who has made it possible to deal with very minute 

 quantities of significant organic substances, such as the pigments 

 of a butterfly's wing. 



In studying the minute structure of cells it is often useful to 

 have differential stains, such as the so-called "basic" stains, which 

 colour more especially the nucleus, and the so-called "acid" stains, 

 which have more affinity for the cytoplasm. It is now beheved that 

 the process is rather physical than chemical, the "basic" dyes being 

 precipitated on the surface of the more solid constituents of the cell, 

 while the "acid" dyes act by soaking or "seeping" in at various 

 speeds. Till recently, however, differential staining was interpreted 

 chemically, and it may be recalled that the possibility of differen- 

 tially dyeing bacteria in a preparation led Ehrlich to the search for 

 a dye which would kill microbes without doing harm to the tissues. 

 In fact, a probably mistaken interpretation led to such valuable 

 drugs as salvarsan and "Bayer 205". 



It must not be supposed that chemistry helps only in regard to 

 physiology. A suggestive instance of the light that chemistry may 

 throw on the problems of development is Dr. E. I. Werber's experi- 

 ment with the developing eggs of the American minnow (Fundulus), 

 which he subjected to various reagents, especially butyric acid, with 

 the result that he provoked many different kinds of monstrosities 

 — in eyes and ears, nostrils and mouth, fins and heart. The butyric 

 acid seems to disarrange, and partly dissolve, the essential germinal 

 material, especially towards the head end; hence monstrosities. 

 Now, it is interesting to note that when the metabolism of carbo- 

 hydrates goes wrong in a mammal's body, one of the results of the 

 disturbance may be (lerivati\es of butyric acid. But if a mam- 

 malian mother's constitution were thus poisoned by the production 

 of butyric acid, this might be the cause of monstrosities in the 

 embryo; a fresh light on a very old problem, and a light coming 

 along what might be called a chemical avenue. 



How can chemistry help with natural history or ecology, the study 

 of organisms in their natural relation to surroundings, both animate 



