iv THE BLOOD : FOKMED CONSTITUENTS 119 



do not exist in blood that has been whipped and defibrinated, and 

 that they disappear from the blood of dogs that have been 

 repeatedly bled, with subsequent infusions of the same blood after 

 it has been defibrinated. In such animals nothing otherwise 

 abnormal can be detected, and the blood -platelets gradually 

 reappear, and are present in their usual number after a few days 

 (Gad). On the theory that the platelets originate in the 

 decomposition of leucocytes, the explanation of these facts may be 

 that the young leucocytes, supplied to the blood by the lymphatic 

 system, require a certain time to develop, become adult, grow old, 

 and disintegrate, when their nuclei give rise to the formation of 

 new platelets. 



On the other hand, not a few of the recent workers in this 

 field incline from many standpoints to the view that the platelets 

 originate from the red corpuscles. 



Koppe, Hirschfeld, and Pappenheim observed that a certain 

 number of erythrocytes are spherical in form, without depressions, 

 within which are masses that stain pink with tri-acid, and faint 

 turquoise with methylene blue, and which when isolated differ in 

 no respect from blood -platelets; while blood -platelets can often 

 be distinguished among the erythrocytes. Other observers hold 

 that the erythrocyte consists of two parts a central, and a peri- 

 pheral stratum. The peripheral layer contains the haemoglobin 

 (Foa) : beneath this lies the true protoplasm. 



It must also be remembered that according to Engel, every 

 non - nucleated blood - corpuscle has at one time or other been 

 one of those nucleated corpuscles of which the mantle contains 

 haemoglobin and is aurantiophile, its chromatin consisting of 

 nuclein, and its achromatic acidophile substance containing 

 protein. When, under normal conditions, the nuclei of the red 

 nucleated corpuscles apparently disappear in kariolysis, the nuclei 

 lose their shape, but the chemical substances of which they are 

 composed persist under other forms. One form of these nuclear 

 rests is the basophile granulation of the erythrocytes (see below) ; 

 the other, more common, form is represented by the almost 

 amorphous blood platelets. On this theory it may be said that 

 every red corpuscle of the depressed form has already lost its 

 platelets, while erythrocytes from which the platelets are on the 

 point of issuing, or in which they are still confined within the 

 corpuscle, are the more nearly spherical. 



This mode of origin of the blood-platelets would account for 

 the appearance they sometimes present of escaping, even where 

 detachment is not complete. The body thus detached may, even 

 if rarely, resemble a nucleus surrounded by protoplasm. 



Foa has recently (on repeating with modern methods of fixing 

 and staining the experiments he made in 1889, in collaboration 

 with Carbone) confirmed the existence of platelets in the spleen 



VOL. i I c 



