TUE BLOOD AND THE LYIMPII. 715 



present fully established, and it appears to me that further proof is re- 

 quired before Ave should admit the existence of crystals from the sub- 

 stances in question, and the more so, because colorless crystals are also 

 formed in the blood, quite independently of the blood-cells. Robin 

 and Verdeil, moreover, assert that they have also obtained crystals 

 from the serum of the blood ; and the quantity of the crystals is by no 

 means opposed to the notion that they arc derived from a salt of the 

 blood merely tinged with Jiconatin, since, in the case of fibrin -we see 

 that not much of a substance is required to occupy a large space. 



§ 223. Physiological remarks. — Tlie development of the bloodvessels 

 takes place, essentially on the same type, in the heart, arteries, and 

 veins. The rudiments of all these vessels, and even of the heart, are 

 solid tracts of cells of greater or less thickness, -which, by the liquefac- 

 tion of their interior substance, and the metamorphosis of the central 

 cells into blood-globules, become cavities, which shortly coalesce, and 

 constitute a continuous passage for the blood. The heart and vessels 

 having remained for some time in this condition of cellular tubes, in 

 which state the former, moreover, exhibits contractions, the cells com- 

 posing the walls, with the exception of the innermost, begin to elongate 

 into fibres, and to represent the divers fibrous tissues and tunics. At 

 the same time the vessels become thicker and increase in circumference, 

 which at first is still to be referred to an increase in the number of the 

 cells, but subsequently, is brought about chiefly, or even solely, by the 

 growth of their elements in length and thickness. In the fifth month 

 of foetal life, all the larger and medium-sized vessels are formed, with 

 their tunics and tissues, and it is impossible to perceive any vestige of 

 formative cells. The tissues, however, appear to be still far from com- 

 pletion, the muscular fibres being short and delicate, and instead of the 

 strong elastic fibrous networks, we perceive only finer and the finest 



* [Reicliert was the first to draw attention to tlie occurrence and nature of crystallized 

 albuminous matters colored with hcematin, in his " Beobaclitungen iiber eine eiweissartige, 

 Substanz in Krystallforni," ]Muller"s " Archiv," 1S49. These were tetrahedrons of as much 

 in some cases as 1-15 of a line long, and occurred upon the placenta and fcetal membranes 

 in a Guinea Pig. Their albuminous nature was confirmed by Schmidt and, Buchheim ; subse- 

 quently, " Bericht,'" IMuller's " Archiv," 1S52, Reichcrt states that he has again found the 

 crystals in the same locality, and that he has convinced himself, by further experiments, 

 that the dilierence observed between his crystals and those described by Kimde and Leh- 

 mann, arose entirely from the action of the spirit in which his first specimens had been 

 preserved. Reichcrt observed die development of crystals of the same kind, though 

 smaller, ia fresh blood taken from the heart of the Guinea Pig. 



In connection with this subject. Dr. Ayres has recorded a very interesting observation 

 with regard to the occurrence of prismatic, more or less red crystals, in a band of olive- 

 green, almost black matter, having the appearance of coagulated blood at the margin of the 

 placenta of the Bitch (" Quarterly Journal of Mic. Science," vol. i. p. 299, with figures). 

 See also the papers of Dr. Parkes (" Med. Times and Gazette," 1852), and of Dr. Sieve- 

 king (" Brit, and For. Med. Chir. Rev.,'' 1853) on this subject.— Tbs.] 



