PROGRESS OF MICROSCOPICAL SCIENCE. 93 



saving epithet ' morpJiologicalli/ ' to the ' identical,' evidently implying 

 some doubt, after all, as to its correctness. 



" In spite, however, of the general acceptation of the opinion, it 

 appears to me to be inconsistent with certain well-known facts. It is 

 my purpose to jH'esent some of these facts, and show wherein they are 

 inconsistent with the theory. I shall consider the subject from 

 Conheim's standpoint : supposing that all j)us originates from white 

 blood corpuscles, although I consider the proof of such sole origin as 

 far from complete. 



" In the first place, it by no means follows that, because a pus 

 corpuscle is derived from a white blood corjiuscle, it is identical with 

 a white blood corpuscle. The white blood corpuscles are mere stages 

 of growth, just as a chrysalis, or a tadpole, is a stage of growth. 

 They have no particular function of their own, as, for instance, the 

 red corpuscles have ; they only exist in order that they may be deve- 

 loped into something else. If this is the case, it is not only supposable 

 that, under the changed conditions of nutrition to which the wandering 

 cells are subjected outside the vessels, they should undergo a change ; 

 but it is difficult to understand how they should continue to be the 

 same that they were within the vessels. 



" Mere similarity of form and appearance is, as we all know, one 

 of the least reliable of resemblances ; and the fact that a pus cor- 

 puscle appears to be like a white blood corpuscle can surely go but a 

 short way towards establishing their identity. The sporules of fungi 

 can often be crushed, and the softer, central portion can be freed 

 from the envelope. When this is done, the central portion of the 

 sporule may resemble a white blood corpuscle so closely in every 

 particular, except, perhaps, in size, that even an experienced observer 

 would be unable to distinguish them apart. Would anyone, on this 

 account, consider them to be identical ? There must be other resem- 

 blances between two bodies besides form and appearance merely, to 

 render them identical. They must correspond in all essential parti- 

 culars ; and if they differ in any essential particular, they plainly are 

 not identical. Now let us see if pus corpuscles correspond in all essen- 

 tial particulars with white blood corpuscles. 



" The white blood corpuscles of every healthy person correspond 

 in every particular with which we are acquainted, with the white 

 blood corpuscles of every other person ; and while there may be, and 

 probably are, points in which the corpuscles of every individual differ 

 from those of every other individual, these differences are so slight 

 that the corpuscles of one person may be substituted for those of 

 another, by transfusion of blood, without distiu'bance of function. 

 If, then, pus corpuscles are the same thing as white blood corpuscles, 

 all pus which has not a specific origin should be similar. I need 

 hardly say, however, that this is notably not the case. IS'o one would 

 sxippose for an instant that the pus from an ordinary abscess, and 

 that from a purulent ophthalmia were the same. Yet the bland 

 and unirritating pus from the abscess, and the highly contagious pus 

 from the purulent ophthalmia, may have had their origin in a simple, 

 and perhaps similar irritation ; and the white blood corpuscles of h 



H 2 



