THE CELL DOCTRINE. 95 



tained in the economy, as in shut sacs, they increase 

 in size, and reach a diameter of .012 millimetre 

 GsflTJ f an i nc h)- Then they fill with fat gran- 

 ules, and are known as corpuscles of inflammation 

 (exudation corpuscles, compound granule cells). 

 Finally the substance and investing membrane of the 

 leucocytes disappear, the granules dissolve and are 

 reabsorbed. 



Capillaries. The finest capillaries are anatom- 

 ical elements of tubular form, with transparent re- 

 sistant walls which measure .001 mm. (.00003937 of 

 an inch) in diameter. These walls contain granular 

 ovoid nuclei, which project, sometimes exteriorly, 

 sometimes upon the inner surface of the tubes. 

 These nuclei measure .006 mm. (.00023622 of an 

 inch) in the transverse, and .008 mm. (.00031596 of 

 an inch) in the long diameter. Their long axis is 

 parallel to that of the vessel. The finest capillaries 

 have a diameter of .007 mm. (.0003756 of an inch), 

 leaving a calibre (after deducting the walls), of .005 

 mm. (.00019685 of an inch), or .002 mm. (.00007874 

 of an inch) less than the average diameter of the 

 blood globules which traverse them. 



They are formed as follows : 1st, In new tissues, 

 hollow projections push out from contiguous cap- 

 illaries, which meet and unite together. 2d, A 

 solid filament forms, in which nuclei make their ap- 

 pearance. Subsequently, the filament becomes hol- 

 low, and its nuclei remain the nuclei of the capillary. 



A single perusal of these views as thus illustrated, 

 will convince the reader that spontaneous formation is 

 the prevailing .mode of origin of the elements of 



