on the Porosity of Bodies. 879 



find either fibres or scales, or both ; the scales composed oi 

 nucleolated nuclei, and these being the elements of fibre which 

 is sometimes seen formed within the scales. 



Mammiferous Red Blood-corpuscles of extreme minuteness, each 

 bearing a Cilium {as described in the Phil. Trans, for 

 1841, pp. 245, 246). 



There was a reason why these discoveries of Keber on the 

 porosity of bodies should have especial interest for me. Since 

 1840, I had been stating facts which showed the material for 

 the elements of tissues, for nutrition, and for the formation of 

 new parts, to be derived from the corpuscles of the blood*. I 

 had also been endeavouring to point out the importance of 

 nucleai self-division. How satisfactory, therefore, to find as one 

 of the results of researches continued for many months by one 

 of the most careful of observers, that the vascular membranes 

 are " not ^ hermetically closed,^ but porous quite through,^' and 

 that the capillaries are *' not ' structureless,' '' but consist of a 

 network of the finest filaments and plates, between which the 

 microscopically perceptible and measurable spaces form a ^'system 

 of the finest hollows and interstices/' sufficient to admit the 

 passage of solid bodies. 



Further, how satisfactory now to be able to refer to a descrip- 

 tion I gave in the Phil. Trans, for 1841, of red blood-corpuscles 

 of extreme minuteness, each bearing a cilium. Regarding these 

 I gave the following particulars. They arise in parent corpuscles. 

 Some of the parent corpuscles are of prodigious size — jq"'. They 

 are always very pale, and sometimes even colourless. You occa- 

 sionally see them ruptured and partially discharged of their 

 contents. In this state they frequently appear shrivelled. When 

 not ruptured they are filled with young corpuscles. These after 

 liberation acquire red colouring matter. Sometimes they become 



* Phil. Trans. 1840, 1841, Edinburgh New Phil. Journal, Oct. 1847. 

 After closely studying the elements of nearly all the tissues of the animal 

 body, I was enabled in 1841 to write as follows : — " Every structure I have 

 examined arises out of corpuscles having the same appearance as corpuscles 

 of the blood. I may here mention, that the tissues submitted to actual 

 observation, with the result just mentioned, will be found to include the 

 cellular, nervous, and muscular; besides cartilage, the coats of blood-vessels, 

 several membranes, the tables, cells, and cyhnders of the epithelium, the 

 pigmentum nigrum, the ciliary processes, the crystalline lens itself, and even 

 the spermatozoon and the ovum. And among the vast number of obser- 

 vations made, 1 have not been able, with the greatest care, to detect a 

 single fact inconsistent with the conclusion above announced. If that con- 

 clusion — which regards the formation of the tissues — be correct, it may, I 

 think, assist us in considering ' the mode in which the floating corpuscles 

 of the blood conduce to nourishment' during life." — Phil. Trans. 1841, 

 p. 217. 



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