INFLUENCE OF THE LIVER IN THE FORMATION OF BLOOD-CORPUSCLES. 129 



this organ, and after this period their share in the production of blood- 

 corpuscles appears to cease. The next point, therefore, to be considered, 

 is the mode in which the subsequent multiplication of the corpuscles thus 

 formed is effected. According to Kb'lliker,* this multiplication in the 

 earliest period of embryonic life takes place, in Mammalia, either by the 

 actual division of each coloured nucleated corpuscle into two or more 

 secondary corpuscles, the number of which is determined by the number of 

 nuclei developed in the corpuscle previous to its division, and which sel- 

 dom exceeds two, though it occasionally amounts to three, or, as figured 

 by Fahrner,f even to four ; or, secondly, by the formation of two or three 

 smaller corpuscles within each large one, which subsequently dissolves away 

 and liberates its brood. Whichever of these modes of multiplication is pur- 

 sued, he considers, however, that it is brought to a complete close so soon 

 as the liver is developed. Then, in his opinion, the production of blood- 

 corpuscles is due entirely to this organ, by whose agency an abundant for- 

 mation of nucleated colourless corpuscles is soon effected, and continues 

 to take place probably through the whole period of embryonic life. The 

 colourless corpuscles thus formed, which are quite different from the 

 colourless embryonic cells found at the first development of the blood, 

 are in all probability converted into coloured blood-corpuscles, either at 

 once, or not until they have multiplied in one or other of the modes just 

 described as happening to the first formed coloured corpuscles. Of the 

 coloured nucleated corpuscles which result from such transformation, the 

 majority flatten, lose their nuclei, and shortly assume all the characters of 

 the ordinary coloured non-nucleated corpuscles found in the blood of Mam- 

 malia. The relative quantity of these latter corpuscles increases in pro- 

 portion to the age of the embryo, so that they soon constitute the principal 

 element of the blood, except of that of the liver, in which, at all periods of 

 embryonic life, colourless and coloured nucleated corpuscles occur in great 

 abundance, owing apparently to the activity of the process of blood- 

 development there taking place. 



The latter part, at least, of this account of Kolliker, was fully confirmed 

 by the results of observations made by Mr. Paget, Mr. Maiden, and 

 the writer. In a sheep's embryo about four inches and a quarter in 

 length, while the blood of the rest of the body consisted almost entirely 

 of ordinary red non-nucleated corpuscles, that from the liver (obtained 

 from a clot drawn from a section of this organ) contained, besides dark 

 red corpuscles, a large quantity of different-sized, pale, granular, and 

 largely nucleated cells, the characters of which were quite distinct from 

 those of the ordinary liver-cells. Still stronger evidence in favour of this 

 view was obtained from the examination of the blood of a human foetus at 

 about the commencement of the fifth month of pregnancy. For, while 



* Henle und Pfeufer's Zeitschrift, 1846, p. 112, et saj. 



t De Globulorum Sanguin. in Mammal. Embryon. et adultis origine. Inaug. Diss. 1845. 



