228 Dr. C. Shearer. On the Oxidation Processes of 



may play in the oxidation processes of the ovum. There can hardly be 

 much doubt, therefore, that its investigation in the future will reveal many 

 new and hitherto unsuspected facts with regard to the oxidations taking place 

 in the ovum on fertilisation. 



V. Summary. 



1. By the use of a special type of the Barcroft differential manometer the 

 oxygen consumption and the carbon dioxide output of the egg of E. micro- 

 tuberculatus has been measured during the period the sperm are actually 

 making their way into the egg. The eggs were fertilised in the closed 

 chambers of the apparatus and their respiration observed before and during 

 fertilisation. 



2. It has been shown that during fertilisation the sperm within a minute 

 of their being added to the eggs bring about an immediate increase in their 

 oxygen consumption. 



3. The study of sections of fixed material of the eggs during the process of 

 fertilisation, shows that within 2 minutes of the sperm being added to the 

 eggs they have not penetrated the egg membrane. They are only in contact 

 with its external surface. 



4. This contact of the spermatozoon with the external surface of the egg 

 membrane, however, is capable of increasing in the space of a minute the 

 oxidation rate of the ovum by something more than 8000 per cent. 



5. During fertilisation there is more oxygen taken up in the first minute 

 of the process than at any subsequent interval of the same time. 



6. The carbon dioxide output of the eggs during fertilisation closely follows 

 the oxygen consumption, the respiratory quotient varying from - 9 to - 95. 



7. The curve of the oxygen consumption of the ovum during fertilisation 

 points conclusively to the stage when the sperm are in contact with the egg 

 membrane as the most important part of the process. 



8. The fusion of the male and female pronuclei in the later phases of 

 fertilisation is correlated with no additional increase in the oxygen con- 

 sumption of the egg-cell. 



9. The oxidation rate of the ovum on fertilisation is probably considerably 

 greater than that of any of the adult body tissues, while the oxidation rate of 

 the mature unfertilised ovum is very much less than that of any adult body 

 tissue. 



10. The ripe sperm and eggs of E. miliaris contain appreciable quantities 

 of the dipeptide glutathione in the reduced (SH) form. In the egg 1 minute 

 after fertilisation it is found in much greater quantity than in the unfertilised 

 condition. It can be washed out of both the fertilised and unfertilised egg. 



