. Chemical embryology. Embryology. SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 621 sketched out by Pott & Preyer. Thus they found that the fertiHsed egg developing with the embryo inside it lost on an average 19-6 per cent, of its weight, and that, if the egg was infertile and was yet incubated, it lost nearly as much (18-5), the difference being about I per cent. This coincides with the fact now definitely known that the main source of weight loss in incubating eggs is the evapora- tion of water, not more than 2 or 3 gm. of solid being burned away. The earliest observer to note that the weight
. Chemical embryology. Embryology. SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 621 sketched out by Pott & Preyer. Thus they found that the fertiHsed egg developing with the embryo inside it lost on an average 19-6 per cent, of its weight, and that, if the egg was infertile and was yet incubated, it lost nearly as much (18-5), the difference being about I per cent. This coincides with the fact now definitely known that the main source of weight loss in incubating eggs is the evapora- tion of water, not more than 2 or 3 gm. of solid being burned away. The earliest observer to note that the weight loss of fertile and in- fertile eggs was much the same appears to have been Erman, who announced it in 1810 in a letter to Oken. Pott & Preyer also made the correct observation that the loss of weight during the incuba- tion period was constant for each day. This, of course, made it ob- vious that the weight loss was. Fig. 105. not directly connected with the embryonic growth, the course of which was known by them to be curvilinear. Fig. 105 is a modification of the illustration they gave of their findings. The weight of water W, they said, evaporated each day by the egg as far as the end of the second week, is equal to the total loss of weight, G, for during this time the weight of carbon dioxide produced, K, is exactly equivalent to the weight of oxygen absorbed, S—other gases being omitted on account of their small quantity. Thus G = r+ W-S and G^W if K^ S. Roughly speaking, these relationships are still true. The question of whether any other gases were given off or taken in during the incubation period by the egg was also handled by Pott & Preyer. Schwann had found that not only carbon dioxide, but also hydrogen and nitrogen, were given off, a result which neither Baumgartner nor Pott & Preyer could confirm. The work which was done later on this point, and which proved that carbon dioxide is the only gas evolved by the developing egg, will be referred to pre
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Keywords: ., bookcentury1900, bookpublishernewyorkthem, booksubjectembryology
