SECT. 222.] DEVELOPMENT OF BLOOD-VESSELS. 527 



former situation, T thought they were formed during life, and I conjectured 

 that they were chemically related to luomatin and hamiatoidin, though their 

 solubility in acetic and nitric acids and in caustic alkalies, showed they were 

 not identical with the latter. Two years later, without knowing my investi- 

 gations, Funke discovered these crystals in the splenic blood of the horse 

 and dog, of man and of fishes ; and thereupon it was found by Kundc {Zeitschr, 

 J', rat. Med. ii., p. 271, 1852), that they are invariably present in the blood of 

 that organ ; and their interesting tetrahedral and hexagonal forms were at the 

 same time indicated by this observer. It is now demonstrated by the careful 

 researches of Funke, that these crystals are only formed outside the body 

 (see Fuxke's Essay, De Sanguine vena IAenalis, Lips., 1851, and his papers in 

 Henxe's Zeitschr. N. Folge, Bd. i., p. 172, and his more recent observations on 

 fishes in the same work, ii., p. 199). Funke gives as his opinion, that these 

 crystals are composed of the globuline of the blood-corpuscles in combination 

 with ha;inatin ; and this view receives confirmation from the complete re- 

 searches of Lehmann, to whom we owe many beautiful experiments on these 

 crystals {Phys. Chem.,i., p. 365, and ii., p. 151, 1853). — For further particulars, 

 I would refer to the writings above quoted, and to my Micr. An/it. ii., 2, pp. 

 585, et. seq., and here I will only add a few brief remarks. The crystals of hasma- 

 to-crystallin (Lehmann) or 'globuline-crystals' as I have named them, are most 

 readily formed by allowing a drop of blood covered with an object-glass to be- 

 come somewhat dried up, or by the slow evaporation of the sediment of beaten 

 blood, which has been diluted with water. They are red or colourless crystals, 

 which assume the form of needles, columns and plates, probably belonging to 

 the rhombic system, but they also occur as tetrahedra, octohedra (guinea-pig, 

 rat, mouse), or as hexagonal plates (squirrel) : they are characterised by their 

 slight stability, disappearing when exposed to the air, and by being readily 

 soluble in water, acetic acid, alkalies, and nitric acid. The crystals are 

 rendered insoluble by alcohol ; yet, on the addition of acetic acid, they swell 

 up to three or four times their original size, returning to their former volume 

 when the acid is washed out (Reichertfs crystals). 



§ 222. Physiological Remarks. — In the development of the blood- 

 vessels, we have first to consider the process as it occurs in the 

 arteries and veins. There it takes place according to two different 

 types. The first type is witnessed in all the primitive embryonic 

 vessels, and probably, also, in many later ones, which develop 

 during the growth of organs; it is also seen in the vessels of the 

 heart. It consists in the formation of solid cellular cords, of 

 greater or less thickness, which are afterwards formed into cavities 

 by the dimuence of their interior portions, and the metamorphosis 

 of their central cells into blood-globules; and these cavities, at 

 first separated, soon coalesce and form a perfect system of canals. 

 The rudimentary heart of the embryo is formed in the same 

 manner, and, even while in this cellular condition, may be seen to 

 perform contractions. When the vessels and the heart have con- 

 tinued for some time in this condition of cell-tubes, the cells of 



