DISCOVERY 



243 



Of course any given attack of sleeplessness may be 

 due to the co-operation of two or more sleef)-banishing 

 factors. Thus if a person is in a state of emotional 

 unrest, this condition acts on the heart, stirring it 

 up to increased effort, with the result that an insomnia 

 is produced which could have been produced bv either 

 factor alone. 



Varieties of sleep related to the vascular factor are 

 the condition in fainting (syncope), and that brought 

 on by compression of the carotid arteries — a method 

 successfully used to induce sleep in a maniac ; both, 

 of course, are abnormal, or, as we say, pathological. 



This is not the place to enter upon the hygienic 

 aspect of sleep and sleeplessness ; but we must allude 

 to the devitalising effects of fatigue especially when 

 coupled with sleeplessness. Both predispose us to 

 ill-health, in that they reduce the resistance of the 

 organism to the onslaughts of the micro-organisms 

 that cause disease. 



The new-born infant sleeps much ; its brain is 

 too immature to perform the functions of full working 

 life, and so more than one-third of its life is passed in 

 sleep. At the other end of life's drama it happens 

 most often that the curtain falls while we sleep, so 

 that Shakespeare was doubly justified in exclaiming, 

 " Our little life is rounded with a sleep." 



REFERENCES FOR FURTHER READING 



Marie de Mendecine. The Physiology , Pathology, and Psychology 



of Sleep. (International Science Series.) 

 Howell. Textbook of Physiology. Chapter on Sleep. 



Animal Fecundity — II 



By F. H. A. Marshall, Sc.D., F.R.S. 



Fellow of Clirist's College, and Reader in Agricultural Physiology in the 

 University 0/ Cambridge 



In considering the factors which control the quantity 

 of offspring produced by animals, it must be borne in 

 mind that the fertilised egg cell, whether of a fish or 

 an insect or any other animal, is the product of union 

 of a single ovum or female reproductive cell with a 

 single sperm or male reproductive cell. The egg, as a 

 consequence of this process, becomes endowed with 

 a new vitality, whereby it is rendered capable of 

 undergoing that long series of cell divisions which 

 results in the full development of a new individual 

 organism. Now in the higher animals the number 

 of eggs which are shed from the female reproductive 

 gland is limited, in some species only a single egg 

 being discharged at a time. In the male animal, on the 

 other hand, the number of reproductive cells produced 

 and shed from the generative gland runs to many 



thousands, the purpose being to increase the chances 

 of the ovum becoming fertilised ; this is an example 

 of the extraordinary prodigality of Nature in seeking 

 to accomplish her ends, the ultimate object in this 

 case being the perpetuation of the race. 



Fecundity of Domestic Animals 



Among the domestic animals, the mare and the cow 

 usually discharge only one ovum at a time, and upon 

 this depends the fact that with these species only one 

 young one is usually produced at birth. With the 

 rabbit, on the other hand, there are sometimes as many 

 as eight ova shed SJ^lchronously from the reproductive 

 gland, and in the pig as many as fifteen or even twenty 

 or more ripe ova are produced. Upon this depends 

 the well-known fact that these animals often produce 

 large litters, the number in each litter generally 

 corresponding closely, but not necessarily exactly, with 

 the number of ova discharged. Since the number of 

 male cells produced is, as a rule, extremely large, it 

 follows that, generally speaking, the female is a more 

 important factor in the quantity of offspring produced 

 than the male. This rule, however, is not invariable, 

 but in a large percentage of instances it is certainly 

 correct. 



Methods of Increasing Fecundity in Sheep 



In the sheep the normal number of ova discharged 

 at a time is not appreciably in excess of the average 

 number of births at the lambing season. This number 

 is most frequently one, but quite commonly two, 

 and sometimes three, but any greater number is 

 unusual. There is direct evidence that in the sheep, 

 as in other mammals which have been studied, a 

 considerable number of ova die within the reproductive 

 gland, and that this may happen at all stages in the 

 development of the ova. Scarcity of available ova at 

 the " tupping" or breeding season may be due either 

 to a retardation in the growth and maturation of the 

 ova, or to an excessive proportion having perished at 

 some previous time, and both conditions must be 

 ascribed to a former want of sufficient suitable nutrition. 

 On the other hand, a favourable nutrition, especially 

 in the period immediately preceding " tupping time," 

 causes a larger number of ova to develop and so to 

 become available for fertilisation, and as a consequence 

 increases the number of births at the succeeding 

 lambing season. What is really the practical applica- 

 tion of this fact has been long recognised by many 

 flockmasters, who have practised the methods of 

 " flushing " or artificially stimulating their ewes by 

 means of an extra supply of special food at the approach 

 of the " tupping " or breeding season. Several years 

 ago the Highland and Agricultural Society of Scotland 



