364 On the Form of the Globules of 



time, then, the discoveries of micrographers were, in some 

 measure, lost to physiology ; and it was necessary, in order 

 to reintroduce them into science, that they should obtain the 

 sanction of modern observers, whose labours bore the seal of 

 those rigorous minds, which will not allow themselves to be 

 convinced until they have acquired all the proofs necessary to 

 convince others. This re-establishment of the microscope in 

 the eyes of physiologists does not go twenty years back, and 

 it is not one of the least services which MM. Prevost and Du- 

 mas have rendered to science by the publication of their re- 

 searches on the blood. 



Among the curious results obtained by these two observers, 

 there is one which, formerly perceived by Hewson, ought 

 especially to interest zoologists, — the coincidence of a certain 

 form in the globules of the blood, and of certain peculiarities 

 in the general plan of the organization of the animals in which 

 they have studied them. In different individuals of the same 

 species, the corpuscles which give to the blood its colour, are 

 all, with very few exceptions, similar to one another, both in 

 relation to their dimensions and their form. In animals of dif- 

 ferent species, their dimensions may vary, and these varieties 

 are sometimes very great, even in beings which, in other respects, 

 have a striking resemblance ; but the form of the globules of 

 the blood only appeared to change from one class to another, 

 and not to vary in the different animals belonging to the same 

 natural division of the animal kingdom. In all the mammi- 

 fera, indeed, submitted to their examination, MM. Prevost 

 and Dumas have constantly found that these corpuscles were 

 circular, and resembled small discs marked with a central 

 spot equally circular ; while in birds, reptiles, and fishes, they 

 have always seen these globules elliptical, and provided with 

 a spot in the centre, of the same form, which appeared to 

 them to be an internal nucleus. 



About the same epoch Rudolphi announced that in the blood 

 of many fishes, such as the perch, the plaice, and the sole, the 

 globules were circular, similar to those of the mammifera ; but 

 more accurate observations have shewn that this physiologist 

 was led into error by the alterations which these corpuscles 

 easily undergo under the influence of water and many other 

 agents. 



