1912.] Examining Normal and Diseased Tissues. 151 



influence of the proteid " radical." But during the period of lactation, under 

 the influence of starvation and phosphorus poisoning, a decomposition of 

 " blood fat " results, and it becomes soluble in ether. That the vital stain is 

 not directly due to the presence of fat or lipoid bodies may also be inferred 

 from the fact that I have hitherto failed to discover a fat or lipoid solvent 

 for any of our vital stains. 



(3) Normal Tissues. 

 ' I quote the following general facts from my first paper : — 

 " Throughout the whole of the animal's tissues the stain is embodied in 

 granules of specific cells. Although the stain circulates in the blood, no 

 blood cell accepts it, nor has it any effect on the cells of the vascular coats. 

 In the skin the stain is discovered in the granules of the fixed connective 

 tissue cells of the cutis, but chiefly in free round cells belonging to the lower 

 layer of the subcutis. Here the cells aggregate in great numbers, and 

 especially in spots where an irritation or lesion of the skin is produced by 

 artificial means or by pathological processes. These cells which belong to 

 the type of the ' histiogenic migratory cell ' are by no means confined to the 

 skin ; they appear in every internal organ (with the one exception of the 

 nervous system) and always in connection with interstitial fibrous tissue. 

 We find them in muscles, tendons, in glands, but especially in serous 

 membranes. The cells display besides marked chemotactic irritability and 

 migratory powers phagocytic properties, which are most obvious in peritoneal 

 lesions of every description. As the granules of their protoplasm eagerly 

 absorb vital stains such as pyrrhol blue, I originally called them pyrrhol 

 cells to emphasise their specific ' vital reaction ' and to distinguish them 

 from the various leucocytic and other migratory cells, which appear in the 

 connective tissue." 



In the course of my newest work I have discovered that the pyrrhol cell 

 is to be found in great numbers in the subcutaneous tissue and the super- 

 ficial muscular layers of the embryo towards the end of its development, and 

 also under the skin and in superficial lymph glands of the new-born animal. 

 Both in new-born and adult animals it is an inhabitant of the bone-marrow. 

 It seems probable that the bone-marrow is concerned in the production of 

 pyrrhol cells. My latest work, especially on the rat, has proved that the 

 matrix of these cells is situated in the tdches laiteuses of the omentum and 

 those of certain peritoneal ligaments, such as the ligamentum gastro-lienale 

 and others. Only by means of the vital stain can we safely and surely distin- 

 guish the pyrrhol cell from its endothelial neighbour, the latter being 

 refractory to the stain. The pyrrhol cell, when leaving the tdche hriteuse, 

 spreads along the perivascular lymphatics into the wide area of the 



