THE BLOOD-PLATELETS 89 



described in circulating blood, though the figures of E. Schwalbe 

 show that bodies which closely resemble those described by 

 Deetjen may be detached from the erythrocytes under the influence 

 of certain toxic substances. The purely histological observa- 

 tions of Preisich and Heim, 1 which rest on the somewhat insecure 

 basis of a special form of staining, lead them to believe that 

 platelets which stain somewhat like the granules of the poly- 

 morphonuclear leucocytes can be seen either separately or in 

 groups of two or three within the red corpuscles. The platelets 

 may even be the actual extruded nucleus or nucleoid-material 

 of the red corpuscles. A somewhat similar view is taken by 

 Schneider, 2 who considers that while a few arise from leucocytes, 

 the chief number originate from the red discs. On grounds of 

 micro-chemical tests, Petrone 3 holds that the platelets are bodies 

 quite different from either the red or white corpuscles. Accord- 

 ing to Heim, the assertion of Mondino and Scala 4 that mitosis 

 occurs in the platelets remains unverified. The experiments 

 of Marino, 5 which were carried out in Mechnikoff's laboratory, 

 possess some interest. He has observed that when rabbit's 

 blood is received into absolute alcohol, platelets are entirely 

 absent, but if the experiment is repeated with alcohol containing 

 varying percentages of water they appear. Within limits, the 

 lower the content of alcohol in the mixing fluid the larger the 

 number of platelets. 



When blood-films are prepared by any of the accepted 

 methods and stained in such a way that platelets, if present, can 

 be recognised, a specimen may show not a single one of these 

 bodies ; another may show a few, but normal human blood in 

 our observations never contains anything like the proportion 

 of one platelet to ten erythrocytes. In the blood of cases of 

 chlorosis an abnormally large number is generally present, while 

 in pernicious anaemia they appear to be entirely absent. In 

 some cases of post-haemorrhagic anaemia a blood-film gives the 

 impression that they are more frequent. Until our knowledge 

 becomes more definite and exact, it appears that the figures 



1 " t)ber die Abstammung der Blutplattchen," Virch. Archiv, clxxviii. 1904. 

 8 " Beitrag zur Frage der Blutplattchengenese. Eine erweitere Nachprufung 

 der Versuche Sacerdottis," Virch. Archiv, clxxiv. 1903. 



3 " Sur le Sang," Arch. ital. de Biologie, xxxvi. 1901. 



4 Arch. ital. de Btologie, xii. 1889. 



" Recherches sur les plaquettes du Sang," Comfites rendus, Sec. de Biologie,. 

 No. 4, 1905. 



