48 MANUAL OF HISTOLOGY. 



According to Recklinghausen, the colorless corpuscles may be generated 

 from the red corpuscles, but it is probable that they may be formed in the tis- 

 sues at many points, and the connective substances through their intimate asso- 

 ciation with the lymphatics are capable of manufacturing them in almost any 

 quantity. Neither of the two varieties of corpuscles, the red or the white, have 

 a cell-wall or outer investing membrane that can be demonstrated, though it is 

 not unlikely that the outer layer of protoplasm has greater density than the 

 more internal portions. 



Wliite or colorless blood- corpuscles. The white blood-cor- 

 puscle is much larger, on an average, in the human species, 

 than the red. It is rounded in form, and is estimated as varying 

 between .0077 and .0120 mm. The average is .0091 mm. (Frey). 

 In contour they are apt to be more or less rough, and exhibit 

 processes. In some of these corpuscles the nucleus is distinct, 

 though when quite fresh a nucleus is rarely seen. If the eye 

 of the observer can watch the corpuscle when it is upon a 

 heated stage and under suitable conditions, its division may 

 be seen. The number contained in the system is variable, as 

 we shall see, depending upon a great number of conditions. 



The personal observations of the author do not incline him 

 to regard the network which has attracted so much attention 

 of late years as satisfactorily shown to exist in living corpus- 

 cles, although there is no question but that it has been seen in 

 corpuscles after exposure to chemical reagents. 



According to Dr. Richard Norris, there is, in mammals, a third corpuscular 

 element which is usually invisible and of the same size as the red ones. Some 

 doubt is thrown upon his alleged discovery, by the fact that the method he 

 employs is likely to produce artificial appearances, and therefore leads to the 

 supposition that the alleged bodies were merely red corpuscles decolorized. 



Mode of counting the blood-corpuscles. Thanks to the 

 instruments of Malassez, Hayem and Nachet, and Gowers, we 

 are in a position to count the red blood-corpuscles with a fair 

 degree of accuracy. 



The methods are somewhat different, but are not difficult to 

 understand. 



Schaefer describes his plans as follows : In order to separate 

 the corpuscles and prevent coagulation, the blood used is first 

 diluted to a definite extent say a hundred times with a 10 

 per cent, solution of sulphate of soda. The mixing can be per- 

 formed in a measuring-glass if the blood is in sufficient quan- 



