409 



biconcave disc in which the less resistant so-called "delle" has been 

 pushed out to form a cup. 



Weidenreich regards a 0.5 ^'jo NaCl solution isotonic for human 

 blood 1). In such a solution he reports "bell-shaped" corpuscles 

 as the preponderating and normal type. In a hypotonic solution 

 they are said to become spherical, and in a hypertonic solution 

 (0.75% NaCl) biconcave discs. Every one is acquainted with the 

 series of transformations through which a red blood corpuscle passes 

 in water. An intermediate stage is represented by a kidney-shaped 

 structure which looks very like shallow cup-shaped forms. What 

 Weidenreich regards as a hypertonic solution is usually considered 

 very close to isotonic-). One would accordingly expect to find in a 

 0.5% NaCl solution exactly such structures as Weidenreich de- 

 scribes. But instead of being normal, they are typical forms for hypo- 

 tonic solutions. Similarly a slightly hypertonic solution yields as an 

 intermediate stage in the production of crenated corpuscles, a cup- 

 shaped form (somewhat smaller than in the hypotonic solutions) due 

 to unequal contraction in "delle" and the thicker rim. 



In a more recent contribution Weidenreich ^) again touches upon 

 the shape of the erythrocytes and seeks to support further his pre- 

 vious claim that they are "Glocken"- or "Napf-Formen". The criti- 

 cisms of Jolly's several observations which seem to contradict those 

 of Weidenbeich appear justifiable with perhaps the exception of the 

 second. Jolly found that fresh blood fixed in a 1 % osmic acid solu- 

 tion contained irregularly bell-shaped cells but no biconcave discs. 

 This appearance Jolly explains as the result of a swelling produced by 

 the osmic acid solution — just what would happen in any hypotonic 

 solution. Weidenreich meets this argument with the observation 

 that when the osmic acid solution is admitted to the drop of blood 

 only after rouleaux have formed the corpuscles are preserved as 

 biconcave discs. If Jolly's argument is valid, Weidenreich holds, 



1) This is the percentage given in a review of the article (loc. cit.) in 

 the Centralblatt für Physiologie for 1902. Lewis referring to the same 

 article gives the figure as 0.65%. But in either case the argument 

 remains the same. 



2) Howell regards a 0.95 "/^ NaCl solution isotonic for mammalian 

 blood (Text Book of Physiology, Philadelphia 1908, p. 917). Accord- 

 ing to Hamburgee (Osmotischer Druck und lonenlehre, Bd. 1, 1902, 

 p. 458) a 0.87% NaCl solution is isotonic for human blood; 0.99 for 

 rabbit blood. 



3) Fr. Weidenrbich, Einige Bemerkungen über die roten Blut- 

 körperchen. Anat. Anz. Bd. 27, 1905, p. 583. 



