174 LECTURE VII. 



cells, yet their membranes may, by means of an aqueous 

 solution of iodine, again be rendered visible, whence it 

 is evident that it was only the high degree of distension 

 and the extraordinary thinness of the membranes which 

 prevented the corpuscles from being seen. Indeed, very 

 violent action on the part of substances chemically dif- 

 ferent is required, in order to effect a real destruction of 

 the blood-corpuscles. If, immediately after they have 

 been treated with a very concentrated solution of salt, 

 water be added in large quantity, we may succeed in 

 bringing things to such a pass that the contents of the 

 corpuscles are abstracted without their swelling up, and 

 their membranes remain behind visible. This was the 

 reason why Denis and Lecanu asserted that the blood- 

 corpuscles contained fibrine ; for they believed that, by 

 treating them first with salt and then with water, they 

 were able to demonstrate its presence in them. This so- 

 called fibrine is, however, as I have shown, nothing more 

 than the membranes of the blood-corpuscles ; real fibrine is 

 not contained in them, although their walls are certainly 

 composed of a substance which has more or less affinity 

 to albuminous matters, and may, when obtained in 

 large masses, present appearances reminding one of 

 fibrine. 



Now with regard to the substances contained in the 

 blood-corpuscles, they happen quite recently to have 

 become invested with great interest in consequence of 

 the more morphological products which have been 

 observed to arise out of them, and which have produced 

 a kind of revolution in the whole theory of the nature of 

 organic matters. I refer here to the peculiar forms of 

 coloured crystals, which can, under certain circumstances, 

 be obtained from the colouring matter of the blood, and 

 which have acquired not only on their own account great 

 chemical, but also very considerable practical, interest. 



