PRINCIPLES OF GENERAL PHYSIOLOGY 



matter for jesting, apart from any real humour. Possibly, the excessive secrecy 

 and reticence maintained on the question are much to blame, and there is no 

 doubt that the wider teaching of a proper physiology in schools will have a 

 good effect in this direction. The almost universal ignorance of matters of 

 the most vital importance to the community, as well as to the individual, is 

 scarcely less than amazing. It is much to be hoped that in the future the 

 sexual process will be looked upon as something essentially beautiful and 

 good, in fact as /cuAos in the old Greek sense, if I may be allowed to use the 

 word again in this connection. The reader will surely not need to be reminded 

 that the love of man and woman has been the motive force of many of the 

 greatest and noblest deeds in the world's history. 



Owing to the very urgency of the impulse for the sake of the preservation of 

 the race, charitable excuse may be made for those who offend ; but condemnation 

 must be unsparingly given to those who tempt others to sin. 



For the reasons given above, I feel unable to agree with the view taken by Sir Thomas 

 Browne (" Religio Medici," vol. i. p. 100 of Sayle's edition, 1904). 



After this apparent digression, for which I offer no apology, we may continue 

 what may perhaps be regarded as the proper subject of our book. In reference to 

 the, as yet, mysterious power of the male cell to excite the process of development 

 in the female cell, the work of Loeb (1900) should be mentioned. This investigator 

 showed that " artificial parthenogenesis " can be produced to a certain extent by 

 treatment of the eggs of sea urchins in various ways. 



The following is the most effective of these. The eggs are first placed for 1'5 to three 

 minutes in a mixture of 50 c.c. of sea water with 2'8 c.c. of O'l molar butyric acid. They are 

 then removed to 200 c.c. of sea water. Fertilisation membranes are formed, but nothing 

 more happens. The next step after the eggs have remained for twenty minutes or more in the 

 natural sea water is to remove them to hypertonic sea water, made by adding 8 c.c. of '2'.") 

 molar sodium chloride to 50 c.c. of sea water. The actual time they require to remain in this 

 solution can only be found by trial, so that samples are withdrawn every five minutes, after 

 they have remained for fifteen minutes. This taking of samples is continued for sixty minutes. 

 Those that have remained for the correct time develop into normal larvae on removal to 

 natural sea water. Further details may be found in the book by Loeb (1909). 



In rare instances, as the well-known one of the bee, where unfertilised eggs 

 develop into drones, natural parthenogenesis is to be met with. It will be 

 obvious, however, that the advantages of mixing the qualities of two individuals is 

 absent in all these cases of parthenogenesis. What we learn from the experiments 

 of Loeb is that it is only under a combination of chemical and physical influences, 

 such as is very unlikely to occur in natural conditions, that the female cell, except 

 in such rare cases as that of the bee, is able to develop without the co-operation 

 of the male cell. In this way the advantage of sexual reproduction, the union of 

 two individuals, is ensured. At the same time, we see that the female cell actually 

 does possess the power of development apart from the entrance of the male cell. 



The work of Przibram on "Embryogeny" (1908) may \te consulted for the laws governing 

 development. 



MENDELISM 



The facts of heredity have, of recent years, become more or less amenable to 

 scientific treatment, mainly by the work arising from that of Mendel, abbot of 

 Briinn. This work was published in 1865, but did not become known until its 

 discovery by De Vries in 1900. 



It is only possible in the limits of space permissible here to give but the merest 

 outline of the fundamental facts. The reader is referred for further details to the 

 book by Bateson (1913). 



In order to be able to follow the process of inheritance from generation to 

 generation, Mendel directed his attention to some single character ; in the Sweet 

 Pea, for example, he took the quality of tallness and dwarfness. Suppose that 

 a tall individual was crossed with a dwarf one, it was found that the next 

 generation consisted entirely of tall individuals. The quality of tallness was 

 called, therefore, "dominant," while that of dwarfness was called "recessive," since 



