THE GENERAL CONSTITUTION OF LIVING BEINGS. 71 



been more or less confounded with the tissues. Neither 

 their function nor their biological characteristics had been 

 defined. Phenomena had been explained without ascend- 

 ing to those corpuscles which are the seat of their begin- 

 ning, v This savant regarded them for the first time as 

 properly forming the subject of a special branch of anat- 

 omy. Besides, he discovered a certain number of them 

 which had till then escaped microscopic observation the 

 perineura in the nerves, the medullocele and myeloplax in 

 the marrow of the bones ; he disclosed the unknown func- 

 tions of several others, such as the leucocytes, the nerve- 

 cellules of the ganglia, the different epithelia ; in a word, 

 he shed new light upon the history of all by describing the 

 peculiarities of their origin and development. 



Nothing is more instructive and attractive than the 

 study of the anatomical elements. They are invisible to 

 our eyes, but they are not the less the glowing centres in 

 which the fire of life burns. It is in and by them that it 

 begins and grows ; it is in them that those fundamental 

 attributes one after another appear, which occasion the 

 highest manifestations of animal existence. Real micro- 

 cosms, each living with its own self-subsisting life, they 

 are endowed with essential properties which explain all 

 vital acts. Their composition from immediate principles 

 is quite complex. It is as inconstant as their structure is 

 delicate : subject to an incessant molecular renewal, assimi- 

 lating constantly new materials, and constantly getting rid 

 of a part of their substance, they are in a state of per- 

 manent transmutation. This perpetual renovation is ex- 

 actly nutrition, the positive mark of organized beings. No 

 life without nutrition. The lowly vibrio nourishes itself as 

 the most complete mammal does ; the meanest mould-spot 

 as the gigantic cedar. All other properties of living bod- 

 ies are subordinated to this one, which is their first condi- 

 tion, and the most specific sign of life. Another charac- 



