18 THE CELL 



living protoplasm. E/einke (II. 32) states that the ^Ethalium 

 septicum gives off ammonia after it has been dried. 



Moreover, the most different metabolic products are always to 

 be demonstrated in protoplasm ; these are produced either by 

 progressive or retrogressive metamorphosis. There is a great 

 similarity shown between the substances occurring in plant and in 

 animal cells. For example, the following substances are found in 

 both, pepsin, diastase, myosin, sarcin, glycogen, sugar, inosit, 

 dextrin, cholesterin and lecithin, fat, lactic acid, formic acid, acetic 

 acid, butyric acid, etc. 



As an example of the quantitative composition of a cell includ- 

 ing its nucleus, Kossel (II. 35) quotes in his text-book, the 

 analysis of pus-corpuscles which was made by Hoppe-Seyler. 

 According to this statement, 100 parts by weight of organic 

 substance contain : 



Various albuminous substances 13-762 



Nuclein 34-257 



Insoluble substances 20-566 



Lecithin and fat 14-383 



Cholesterin , . 7-400 



Cerebrin 5-199 



Extractives 4-433 



Phosphorus, sodium, iron, magnesium, calcium, phosphoric 

 acid and chlorine were found in the ash. 



As regards the physical properties of protoplasm, streaming 

 protoplasmic threads are sometimes noticed in which double re- 

 fraction is seen, the movements being for the most part in a 

 direction such that their optical axes coincide (Engelmann). 



d. The more minute Structure of Protoplasm. Proto- 

 plasm was denned above as a combination of substances, the most 

 minute particles of which we must picture to ourselves as united 

 together to form a complex structure. Investigators have en- 

 deavoured to discover more about this marvellous structure, partly 

 by speculation, and partly by microscopical observation. 



As to the first, Nageli has made some important suggestions, 

 a more detailed account of which is given later in the section 

 entitled " The Molecular Structure of Organised Bodies." 



As to the second, numerous investigators, amongst whom From- 

 mann, Flemming, Biitschli and Altmann are conspicuous, have 

 recently been working at the subject. Living protoplasm, as well 

 as that which has been killed by special reagents, has been 



