i62 EMBRYOLOGY IN THE SEVENTEENTH [pt. ii 



is important because it is the first book in which definite chemical 

 experiments on the developing embryo are reported, and also 

 because it contains the first practical instructions for dissections of 

 embryos. 



Sir Thomas Browne had, as we have already seen, made experi- 

 ments of a chemical nature on the constituents of birds' eggs and of 

 the eggs of amphibia, but he did not analyse them after any develop- 

 ment had been allowed to take place. He may therefore be regarded 

 as the father of the static aspect of physico-chemical embryology, 

 while Walter Needham may be regarded as the founder of the 

 dynamic aspect. The practical difficulties of these pioneers of animal 

 chemistry may be seen in such a book of practical instructions as 

 Salmon's General Practise ofChymistry of 1678. They had no satisfactory 

 glassware, no pure reagents, the methods of heating were incredibly 

 clumsy, and there was no means of measuring either heat or atmo- 

 spheric pressure. 



In the review of Needham's book which is to be found in the 

 Philosophical Transactions of the Royal Society for September 1667 there 

 occurs the sentence, "These humors (the amniotic, allantoic, etc.) 

 he saith, he hath examined, by concreting, distilling, and coagulating 

 them; where he furnishes the Reader with no vulgar observations". 

 What were these observations ? They are to be found in the chapter 

 entitled "The nature of the humours": 



"I now proceed to speak of this other nutritive liquor round about 

 the urine itself which latter is plainly separated by the kidneys and 

 the bladder. These liquors also proceed from the blood and seem 

 similar to its serum but yet they are different from it. For when fire 

 is applied to them in an evaporating basin [cochlea] they do not 

 coagulate, as the blood-serum always does. Indeed, not even the 

 colliquamentous liquid of the egg itself coagulates in this manner, 

 although it is formed from juices which are evidently liable to coagu- 

 lation — in the same way humours differ from themselves before and 

 after digestion, filtration, and the other operations [mangonial of 

 nature. All, when distilled, give over a soft and clear water [mollem 

 et lenem] very like distilled milk. This property is common to the liquor 

 of the allantoic space, along with the rest. Because when the salts 

 are not yet made wild and exalted the serum of the blood remains 

 still quite soft and does not give proof of a tartaric or saline nature. 

 Indeed, the first urine of an infant is observed by nurses to be not at 



