THE BLOOD-PLATELETS 85 



writers, for the whole subject is beset with difficulties. Renewed 

 interest in the subject originated with Deetjen's discovery in 

 1901 of a new method for studying the platelets; but while 

 many observers agree that these exist in living blood, a great 

 difference of opinion prevails as to the origin of these bodies 

 both within and outside the body. Not only is there a difference 

 of opinion as to the existence of platelets in living blood, but 

 most irreconcilable views have been advanced to explain the 

 origin of these puzzling bodies. 



First View. — The haematoblasts of Hayem, or platelets of 

 Bizzozero, or thrombocytes of Dekhuyzen, are independent 

 bodies or cells which exist in normal living blood. They are 

 of equal morphological importance to the red and white cor- 

 puscles. In mammalian blood they possess certain peculiarities 

 which distinguish them from the nucleated, spindle-shaped, 

 homologous bodies in amphibian blood. 



Second View. — They are not pre-existent structures in normal 

 blood, but are artefacts. They may, and frequently do, occur 

 in disease, either as a consequence of disease or damage to the 

 blood or the vessels which contain it. The blood-platelets are 

 separations from the blood-plasma, being of the nature of a 

 molecular deposit of one or more of the proteids of the plasma. 

 From the fact that they possess a relatively large amount of 

 phosphorus they may be composed of nucleo-proteid. 



Third View. — The platelets are pre-existent bodies in circu- 

 lating blood, and their number varies both in physiological and 

 pathological conditions. They are in no sense equal in mor- 

 phological importance to the red and white blood-corpuscles. 

 They are either extrusions from or fragment of the leucocytes 

 or erythrocytes — in the latter case they will possess haemo- 

 globin, and may contain an inner body or nucleoid, which 

 is a remnant of the nucleus which the erythrocyte contained in 

 an early stage of its development. The Blutplattchen, therefore, 

 may be found in any one of four different types : 



1. Platelets with haemoglobin and an inner-body. 



2. Platelets with haemoglobin and no inner-body. 



3. Platelets without either haemoglobin or an inner-body. 



4. Platelets without haemoglobin and with an inner-body. 

 According to E. Schwalbe, 1 the author of this grouping of the 



1 Virchozti's Archiv, clviii. 1S99, clxviii. 1902 ; Wiener vied. Rundschau^ No. 10, 

 1903 ; Ergebnisse der allg. Pathologie, xiii. 1902 (full literature). 



