1871.] Blood-corpuscles through the Walls of the Vessels. 557 



perforation of the capillaries by the morphological elements of the blood, 

 viz. the red and white corpuscles. 



These observations attracted little attention till the year 1867, when the 

 facts made known by Dr. Waller were rediscovered by Professor Cohnheim, 

 of Berlin. 



Since the publication of Cohnheim's researches very considerable interest 

 has been taken in the subject, and the experiments have been repeated and 

 the facts corroborated by eminent physiologists and pathologists in all 

 parts of the world. 



On a careful consideration of the hypotheses which have been propounded 

 by Waller, Cohnheim, Strieker, Bastian, and Caton, to account for the 

 curious phenomena in question, it will be found that all these hypotheses fall 

 short in one important particular, inasmuch as they afford no explanation 

 whatever of by far the most singular part of the process, viz. the fact that 

 the apertures through which the corpuscles pass again close up and 

 become invisible. The question, indeed, is not so much how the cor- 

 puscles get out, as how they get out without leaving any permanent trace 

 of the apertures through which they have so recently passed, and which 

 were so palpable during the period of transit. 



Before proceeding to elaborate my own views, it may be well to restate 

 succinctly the various points upon which observers are agreed. 



1st. Both white and red corpuscles pass out of the vessels through 

 apertures which can neither be seen before their ingress into or egress 

 from the vessel wall, but only during the period of transit. 



2nd. An essential and primary step in the process is, that the corpus- 

 cles shall adhere or, more properly, cohere to the wall of the vessel. 



3rd. These cohering corpuscles shall subsequently be subjected to pres- 

 sure from within. 



With these conditions fully before our minds, we will proceed to inquire 

 if in physics we can find the analogue of these seemingly mysterious phe- 

 nomena. 



In the first place, this phenomenon of the passage of bodies through 

 films or membranes is by no means confined to the capillary walls, the 

 same thing has been observed in nucleated blood-corpuscles, such, for ex- 

 ample, as those of the frog. In these cases no rupture or aperture of exit 

 has been discovered. 



It is obvious that the escape of the nucleus from its capsule without 

 rupture, and the passage of the entire blood-corpuscle through the capil- 

 lary wall without rupture, are phenomena of the same class ; and the ex- 

 planation which will suffice to clear up the one, will also apply with equal 

 force to the other. 



As a matter of fact, it will be admitted that we can form no h priori 

 conception of one form-retaining body passing through another without 

 either rupturing it or distending certain holes or pores which it may al- 

 ready possess. This, however, is just one of those cases in which con- 



