262 NATURE AND LIFE. 



own structure, its specific energy, its mode of nutrition, its 

 fixed secretions characteristics, moreover, which vary with 

 circumstances and media. Yet we can point out more than 

 one interesting similarity between certain ones of these 

 species, which seem to discharge quite distinct functions, 

 and hold very unlike stations, in the vast harmony of vital 

 monads. The cells of fruits, when placed in certain condi- 

 tions, behave, as has been seen, like the cells of brewer's 

 yeast ; they both decompose sugar and yield alcohol. We 

 may trace resemblances not less close, as Blondeau and 

 Pasteur have done, between acetic mycoderms and blood- 

 globules. Both alike serve as carriers of oxygen the first 

 for the slow combustion of alcohol ; the last, for the slow 

 combustion of the albuminoid matters in animal tissues. 

 It is even likely that there is a principle in mycoderms 

 similar to hemoglobine in the blood-globule, and provided 

 with a special affinity for oxygen. However this may be, 

 comparisons of this kind open a new path for physiology. 

 As that science is definitely summed up in the explanation 

 of existences and processes in the microscopic elements of 

 organs, it is plain that nothing can be more useful to it 

 than the study of these one-celled organisms in which the 

 phenomena are extremely simple, and life is reduced, in a 

 manner, to its primitive factors. It becomes more and 

 more evident that progress in the comprehension of the 

 superior animals is bound, with the very closest ties, to ad- 

 vance in the comprehension of the mechanism of nutrition 

 in the rudimentary units of life, in the smallest beings that 

 it is given us to study. 



II. 



Now, whence come those organized microscopic corpus- 

 cles to which, as we have seen, very many of the alterations 

 of organic matter must be attributed ? Upon this great 

 problem, opinions at this day are still very contradictory. 



