460 OF NUTRITION. 



blood, with softly shaded contours and numerous granules in their interior. 

 They contain one, two, or more nuclei. By Virchow 1 they were considered 

 to be derived essentially from the proliferation of epithelial cells, and of con- 

 nective-tissue corpuscles, and there can be no doubt that all intermediate 

 stages between healthy epithelial cells and connective-tissue corpuscles, and 

 pus-corpuscles, may be traced in inflammation, but numerous observers have 

 noticed that under certain altered physical conditions of the circulation, an 

 escape, both of the white and of the red corpuscles, takes place from the in- 

 terior of the vessels into the adjoining tissues. This phenomenon was first 

 observed in 1843, by Dr. W. Addison, 2 and was noticed to occur in inflam- 

 mation by Waller, 3 who in a remarkable memoir fully corroborated Addi- 

 son's observation, declaring that he had seen the corpuscles protruding half 

 out of the vessels ; whilst Addison had already arrived at the conclusion that 

 pus-corpuscles of all kinds were only altered colorless blood-corpuscles. 

 These statements, however, received little attention till the publication of 

 Cohnheim 4 of an essay on inflammation, in which he described the process 

 of the passage both of the white and red corpuscles through the walls of the 

 capillaries, and even of tolerably thick-walled veins, in detail. Cohnheim's 

 observations immediately attracted great attention, and though they have 

 been opposed by Feltz, 5 Picot, fr and a few others, they have received the 

 support of so many good observers, as of Strieker, 7 Prussak, 8 Caton, 9 Nor- 

 ris, 10 Bastian, 11 and Heller, 12 that the main fact of the escape of the cor- 

 puscles from the vessels may be regarded as incontrovertible. In a recent 

 essay, Cohnheim 13 has given his latest views upon the point. The passage 

 of the white corpuscles through the walls of the vessels appears to be due to 

 some physical alteration in the walls of the vessel, reducing their tenacity, 

 and permitting the colloidal substance of the corpuscles to penetrate them 

 in a mode essentially similar, as Norris showed, to that by which a solid body 

 may be made to traverse the thin film of a soap-bubble. This process is 

 probably aided by the amoeboid movements of the white corpuscles, and in 

 part also by the increased pressure of the blood. 1 * That neither the increased 

 pressure of the blood, nor the mere dilatation of the vessels is sufficient per 

 se to lead to the emigration of the corpuscles, seems to be demonstrated by 

 the fact that if any slight injury, as a pinch of moderate severity, be inflicted 

 on a transparent structure, as the tongue of a frog, the vessels in the vicinity 

 may be seen immediately to enlarge (the arteries being first affected), per- 

 mitting a more rapid current to flow through them. The veins then en- 

 large, and afterwards the capillaries. This condition is maintained for 

 some minutes, when the arteries begin to contract, and with the capillaries 

 return to their normal condition. The veins, however, do not follow this 

 process of contraction, and hence the blood-current in them becomes slower. 



1 See his Cellular Pathology, passim. 



2 Exper. and Fract. Researches on Inflammation, 1843. 



3 Philosoph. Magazine, Oct. and Nov. 1846. " Virchow's Archiv, 1867. 



5 Robin's Journ.'de 1' Anatomic, 7 me Annee, 1870-71, pp. 33 and 505. 



6 Idem, p. 4r,r>. ' Strieker, idem, No. 6, 1867. 

 s Prussak, Sitzungsber. d. Wien. Aknd., Bd. Ixvi, p. 13. 



9 Caton, Journal of Anatomy and Physiology, 1871, vol. v, p. 35. 



10 Morris, Proceed. Koy. Society, 1871, No. Y'JO. 



11 Haitian, Transactions of Pathological Society, 18f>8, vol. xix, p. 4G1. 

 - Hdlcr, Ontralblatt f. d. Med. Wiss., 1870, p. 310. 



13 Colmhi-im, NIMH- Untersuchungen uber Entzundung, Berlin, 1873. 



" It is possible, as I'm-ves (Centralblatt f. d. Mod. Wis., 1874, p. 654), Arnold 

 (Virchow's Archiv, 1873, Bd. Iviii, 203), Thomas (Centralblatt, 1874, p. 3f,4), and 

 some writers maintain, that pores, which they believe are naturally present between 

 the epithelial cells of which the walls of the smaller vessels are composed may enlarge, 

 but this requires further confirmation. 



