iNTRACBLLULAE DIGESTION OF INVERTEBRATES. 103 



the phenomena of inflammatory exudation in Vertebrates. In 

 both cases a number of mesoderm cells collect round the irri- 

 tating body, and act upon it as best they may. The difference 

 between the two cases is only one of degree. In Bipiunaria, 

 which has as yet no trace of a vascular system, we see a gra- 

 dual accumulation of the numerous amoeboid cells, which are 

 scattered tbroughout the mesoderm ; while in molluscs the 

 lacunar blood-vessels play a purely passive part in allowing the 

 corpuscles to flow through them. In Terebella, with its closed 

 blood system and red plasma, inflammation^ aftects only the so- 

 called lymph corpuscles of the body cavity ; if the blood-vessels 

 be not injured by the intrusive body, no transudation occurs, 

 as is evident from the absence of coloration. Therefore, from 

 the point of view of comparative pathology, Cohnheim's dictum, 

 '' without vessels no inflammation,"^ which has been accepted 

 by many pathologists, does not bold. Inflammation is a phe- 

 nomenon phylogenetically much older than blood-vessels, while 

 exudation is a comparatively late development. From this 

 point of view, it is evident that the white corpuscles of Verte- 

 brates must be regarded as of more importance than has been 

 thought to be the case, thus justifying the views of Thoma.^ 



Our observations on resorption during metamorphosis among 

 Echinoderms (which are in complete harmony with the results 

 of histological and pathological investigation on Vertebrates^) 

 have taught us that mesoderm cells are able to take up and. to 

 digest albuminoid granules. This conclusion is strengthened 

 by the following observations. 



If we follow the fate of (human) blood- corpuscles, after their 



' I have so far had uo opportunity of examining the phenomena of inflam- 

 mation in those annelids which possess well developed blood-corpuscles ; I 

 hojje shortly to fill up this gap in my observations. 



^ "Ueber Entziindung und Eiterung," ' Virchow's Archiv,' 1867, Bd. 40 ; 

 compare also his 'Neue Untersuchungen liber die Entziindung,' Berlin, 1873, 

 p. 11, 42, 62, 67, 71. 



^ " Ueber Entziindliche Storungen des Capillarkrieslaufs bei Warmbliitern," 

 •Virchow's Archiv,' Bd. 74, p. 386. 



* Summarised by Ziegler in his ' Lehrbuch der pathologischen Anatomic,' 

 2 Aufl., Bd. i, 1882, pp. 167-175. 



