Note 869 — Chapter V · (continued 3)

‘In seeking to determine the respective importance of the different constituents of the blood, by the philosophical and most difficult inquiry into their respective periods of formation in the development of the embryo, Hunter made the interesting discovery that the vessels of the embryo of a red-blooded animal circulated in the first instance colourless blood, as in the invertebrate animals. ‘The red globules,’ he observes, ‘seemed to be formed later in life than the other two constituents, for we see while the chick is in the egg the heart beating, and it then contains a transparent fluid before any red globules are formed, which fluid we may suppose to be the serum and the lymph.’ I well remember the feelings of surprise with which I listened, while at Paris in 1832, to a memoir read before the Academy of Science, by MM. Delpech and Coste, the object of which was the announcement of the same fact as a novel and important discovery. The statement of the French observers was received with all the consideration which its importance justly merited, without its being suspected that our great physiologist had, half a century before, embraced it, with all its legitimate deductions, in the extended circle of his investigations.’ Owen's Preface to vol. iv. of Hunter's Works, p. xiii.