MALPIGHI 159 



pendente, and Harvey had gone before ; none of them, 

 however, had made more than a sketch of this memorable 

 history. Aristotle had remarked the beating heart of 

 the early chick and the direct absorption of the yolk. 

 Fabricius made little further progress ; he derived the 

 embryo from the chalazae (twisted cords of albumen 

 which project from the yolk-bag). Harvey did much 

 more ; he described the ovary and oviduct of the hen, 

 the new-laid egg, the sequence of events during the 

 early days of incubation, and the escape of the chick 

 from the egg. He also noted the vessels which bring 

 nourishment from the yolk, and the first steps in the 

 formation of the brain. Malpighi enjoyed one great 

 advantage over his forerunners ; he was able to use 

 magnifying glasses in the work. In his memoirs on the 

 chick we find clearly delineated the vascular area, the 

 dorsal folds, the mesoblastic somites, the vesicles of 

 the brain, the amnion and allantois, the development 

 of the heart (traced in great detail) and the aortic 

 arches, which in a particular stage are seen to encircle 

 the gullet. More minute and technical details are also 

 shown and described. 



In his treatise De Formatione Pulli Malpighi notes 

 that an embryo can be distinctly seen in an unhatched 

 egg, and figures a second-day chick extracted from such 

 an egg. He mentions one circumstance which renders 

 all plain ; this particular egg was opened in August, and 

 in a season of unusual heat, even for Italy, a heat 

 sufiicient, no doubt, for development. Malpighi inferred 

 that the rudiment of the embryo goes back further than 

 had been supposed. ^ 



* " Quare pulli stamina in ovo praeexistere, altioremque originera nacta 

 esse fateri oonvenit, haud dispari ritu ao in Plantarum ovis " (De Formatione 

 Pulli, p. 2). This observation formed a foundation-stone of the amazing 

 theory of predelineation and emhoUement (infra, p. 289). 



