94 PROGEESS OF MICROSCOPICAL SCIENCE. 



two individuals may preserve their similarity at the same time that 

 the pus shows such great differences. Can things which differ from 

 each other both be similar to the same thing ? 



" Again, the physiological action of pus differs from that of a white 

 blood corpuscle. White blood corpuscles may easily, and with safety, 

 be transferred from the vessels of one individual to those of another ; 

 but if pus is injected into the vessels, the result is a serious disturb- 

 ance. The experiment has been tried of injecting pus into the veins 

 of an animal ; a febrile action, dangerous to the life of the animal, is 

 the result ; and if some of the blood of this animal is injected into the 

 veins of a second animal, a still severer disturbance than in the first 

 animal is set up. If the blood of the second is injected into the veins 

 of a third, a similar disturbance is set up ; and so of a fourth, and so 

 on. The introduction of pus into the veins of the animal has given 

 rise to profound changes in its blood — an effect differing widely from 

 the harmless result of the introduction of the blood corpuscle, 



" Again, the white blood corpuscles can become organized, and 

 form tissue ; or, at least, the wandering cells outside the vessels can 

 become organized; and it is a well-known fact, that from these 

 wandering cells all inflammatory new formations arise. Some, indeed, 

 maintain that from such wandering cells are produced all the new 

 growth of connective tissue, and all the new formations in the body. 

 Pus, however, cannot become organized, as anyone who has observed 

 the mischief done by a small quantity of pus beneath the periosteum 

 of a finger can well appreciate. 



" If pus, then, originated from a white blood corpuscle, it has lost 

 the power of organizing ; and w])o can tell how great is the difference 

 which has resulted from that loss ? 



" Again, if the pus from our purulent ophthalmia, which may have 

 arisen from a simple irritation, be introduced beneath the lid of a well 

 person, it will, in all probability, set up a disease similar to that in 

 the eye from which it was taken. If a white blood corpuscle had the 

 property of setting up disease, what surgeon would be skilful enough 

 to avoid purulent ophthalmia? The pus from purulent ophthalmia, 

 then, has not only lost the power of organizing, but has acquired 

 noxious properties, which render it hurtful to the person in whom it 

 originated, and dangerous to those with whom it may come in contact. 

 Can any two things differ more widely than the blood corpuscle and 

 this pus — the one a useful and necessary part of the body, and the 

 other a breeder of disease, and an object to be dreaded ? 



" In what I have said, gi-antiiig what I do not believe, that all pus 

 originates from white blood corpuscles, I have tried to show : — 



" 1st. That white blood corpuscles, being in a transition stage, we 

 have no right to expect that, in the changed condition of nutrition to 

 which they are subjected, outside the vessels, they would continue to 

 be the same that they were within the vessels. 



" 2nd. That mere similarity of appearance was insufficient evidence 

 of identity. 



" 3rd. That different samples of pus are unlike each other ; which 

 they would not be if they were white blood corpuscles. 



