THE REPRODUCTIVE GLANDS. 455 



stance is present which on boiling with water yields a material sim- 

 ilar to cartilaginous glutin. A mucinous substance is found about 

 the sixth day, but it subsequently disappears. The amount of 

 haemoglobin steadily increases in its relation to the body-weight. 



Levene has recently shown that incubated eggs contain rnono- 

 amido-acids, and he regards it as probable that the preparations 

 which he obtained consisted of an equimolecular mixture of mono- 

 amido-butyric acid and mono-amido-valerianic acid. The results 

 were obtained with eggs that were twenty-four hours and seven 

 days old. 



Interesting also are Levene's observations on the amount of albu- 

 mins at different stages of development, which were made on fish 

 eggs. Non-incubated eggs contained 66 per cent, of albuminous 

 nitrogen ; after twenty-four hours' incubation, 53.57 per cent, was 

 found ; after ten days, 64.79 per cent ; and at the expiration of 

 nineteen days, 71.84 per cent. During this period there was also a 

 steady increase in the amount of nitrogen referable to non-albu- 

 minous substances that could be precipitated with phosphotungstic 

 acid, viz., from 12.07 to 28.25 per cent. 



On the basis of Spitzer's observations on the nature of the oxida- 

 tion-ferments as nucleoproteids Lob expressed the opinion that the 

 nucleus represents the organ of oxidation of living matter, and that 

 cellular matter devoid of nuclei is incapable of regenerating its kind 

 for the reason that its power of oxidation is too insignificant. 

 Jacoby, however, has shown that in pig embryos, at least at a time 

 when the first indications of the formation of a bony skeleton exist, 

 aldehydase at any rate cannot be demonstrated. Whether or not 

 it is present as a zymogen, has not been investigated. Later the 

 aldehydase appears, viz., in embryos which are 9 cm. long and 

 longer. A tangible basis for Lob's assumption hence does not 

 exist. 



The chemical composition of the allantoic fluid and the amniotic 

 fluid has already been considered. 



The placenta has not as yet been studied in detail, but it is likely 

 that its greater portion consists of collagen, in accordance with its 

 fibrous structure. In its marginal zone two pigments have been 

 encountered which apparently are related closely to bilirubin and 

 biliverdin, and are derivatives of haemoglobin. The orange pigment 

 may be obtained in crystalline form, while the green pigment, which 

 has been termed hcematochlorine, is amorphous. 



