368 Veterinary Obstetrics 



have occasion to mention some of these aberrations in develop- 

 ment when dealing with the defects of the new born animal. 



While the subject of teratology is one of very great scientific 

 interest and serves largely to emphasize the facts of embryo- 

 logy and the regularity with which the development of the 

 embryo ordinarily proceeds, we must content ourselves, in this 

 treatise, with a bare mention of the subject. Teratology was first 

 placed upon a scientific basis by Gurlt fLehrbuch der patho- 

 logischen Anatomic, 1831) and later the science was expanded 

 by Saint Hilaire and others. 



Experimentally, teratology has also received a considerable 

 amount of attention and it has been found that the chick embryo 

 and others which are readily available for manipulation may be 

 caused to undergo a great variety of aberrations during the early 

 stages in development, by mechanical disturbances. The con- 

 clusion has been reached, from these experiments, that accidents 

 of a somewhat similar character, occurring during the very early 

 stages of embryonic development in our higher animals lead also 

 to aberrations in development. 



It is worthy of remark that those arrests in the development 

 which have occurred early in the life hist.ory of a given embryo 

 show a marked tendency to recur in the offspring of the defective 

 organism, when it lives to the breeding age. This may readily 

 occur in the milder forms of aberration in development, but it is 

 only rarely that the more serious ca,ses, which we generally speak 

 of as monstrosities, are capable of breeding, or even of surviving 

 to the adult period. In the lesser aberrations in development, 

 such as arrests in the closure of the umbilic or inguinal rings, 

 resulting in hernia, the defect is extremely liable to become 

 fixed and to be reproduced with disastrous frequency in the off- 

 spring of such an animal. 



Among the laity, the occurrence of monstrosities arouses more 

 or less mysticism and they are frequently attributed to some 

 psychic influence upon the pregnant mother, usually at some 

 late period in gestation, when the defect has already long been 

 fixed in the fetus, having occurred at a very much earlier date. 

 On the other hand, it is highly probable that teratology itself 

 has had an important influence upon mythology and may have 

 played an important part in such myths as the Cyclops, the 

 Janus and others, which myths find accurate representatives 

 among the monstrosities in man and in animals. 



