( 146 ) 



The selection of' the indifferent substance carbon, instead of the 

 usual grains of carmine was based on the greater facility and more 

 accurate certainty with which the taking up of' carbon can be 

 ascertained. It was also for this reason that carbon had been the 

 substance selected in former investigations on the action of carbonic 

 acid ') and the action of' cyanate of potassium a ) on phagocytosis. 



On the present, as well as on the former occasion, the leucocytes 

 used in our investigations, were taken from the blood of a horse 3 ). 

 They were obtained by shaking blood with pieces of' glass in a 

 closed bottle and straining the defibrinated blood through a piece 

 of' muslin. The red corpuscles sink to the bottom, and the serum 

 which covers them holds all the leucocytes. When this turbid fluid 

 has been poured off we have a suspension of leucocytes in serum ; 

 this suspension can be made richer in leucocytes, by centrifugal izing 

 it, removing part of the clear serum and mixing the leucocytes 

 which have fallen to the bottom, with the remaining serum. A detailed 

 description of this method, the process of' preparing the carbon, 

 the mode of bringing it into contact with the leucocytes, and the 

 method of' determining the percentage of the cells which have 

 taken up carbon, will be found in our article in the Biochemische 

 Zeitschrif't 4 ). 



II. The effects froduced on phagocytosis by the addition of water. 



Our first experiments were directed to the solution of the question 

 in how far phagocytosis is affected by the addition of water. 



With this object in view, equal quantities of the suspension of 

 leucocytes were mixed with serum, previously diluted with known 

 quantities of water. The following table shows the results of one of 

 the series of experiments. It will need no further explanation. 



J ) Hamburger. Virchow's Archiv, 156, 1899. S. 329. Osmot. Druck u. Ionen- 

 lehre. 1. S. 416. 



-) Hamburger. Het gedrag van witte bloedlichaampjes tegenover Gyaankalium in 

 Rosenstein's Feestbundel. 1902. 



, 3 ) At Groningen we experienced great difficulty in obtaining a regular supply 

 of horses' blood. Mr. K. Hoefnagel, the Director of the abattoir at Utrecht, had 

 the great kindness fully to meet our wants, for which we here beg to tender him 

 our best thanks. 



*) Compare also Hamburger, Osmot. Druck u. Ionenlehre, Bd. 1. S. 401. 



