505 



erroneous, that it would be mere waste of time to give any lengthened 

 consideration to his paper. 



That by the experiments I have detailed one mode of origin of 

 pus corpuscles is established beyond question, I think must be admitted ; 

 but at the same time I think it would be premature to affirm that this 

 is the only way in which these bodies arise. Still we must allow that 

 Cohnheim made a most remarkable and fruitful discovery, when he 

 found that the white corpuscles can traverse the walls of the vessels 

 without injury to the latter. 



The importance of this discovery is not confined to the process of 

 suppuration only ; for there can be no doubt that, under favourable 

 circumstances, the extravasated corpuscles may undergo development, 

 and take part in the formation of tissues or new growths ; and already ob- 

 servations and experiments have been made, showing that in the healing 

 of wounds and other processes besides those of suppuration the emigrated 

 white blood cells play a most important part. In several cases, too, 

 where great difficulty was formerly experienced in accounting for the 

 origin of pus by deriving it from the pre-existing cells of the inflamed 

 part, the theory of Cohnheim offers welcome assistance. Pneumonia, 

 in which the air vesicles of the lungs become filled with exudation, 

 composed mainly of pus cells, is such a case. Quite recently, Axel 

 Key has proved, by the injection into the blood of coloured substances, 

 so as to mark the white corpuscles, and examination of the exudation 

 in a subsequently excited pneumonia, that the pus corpuscles in the 

 latter contained coloured particles, and were, therefore, derived from 

 the blood. The great abundance of capillary vessels about the air spaces 

 of the lung will account for the well-known rusty colour of the sputum 

 in pneumonia. 



This has long been recognised as dependent on the presence of red- 

 blood corpuscles ; and it will be remembered that through the capillary 

 walls red as well as white corpuscles have been seen to pass. 



I hope in a future communication to report on the process of inflam- 

 mation in the cornea ; my observations on this tissue have hitherto not 

 given decisive results. 



