412 F(ETAL DYSTOKIA. 



begun to be so developed, only became a,nomalous and monstrous 

 because their development was disturbed. Therefore these anomalies 

 did not exist previous to impregnation, but were the result of some per- 

 turbation occurring during the development of the embryos, which were 

 at first perfectly normal. 



The opinion which at present prevails with respect to these malforma- 

 tions, is to the effect that the embryo or foetus has been submitted to 

 some kind of alteration in utero, and that this has been produced during 

 the interval between conception and birth. It is a matter of ordinary 

 observation that sometimes a fall, blow, sudden fright, or a powerful 

 mental impression will, in woman, disturb the ordinary course of preg- 

 nancy, and give rise to more or less unusual symptoms, and even prema- 

 ture birth of an imperfect foetus. It has been attempted to explain the 

 action of these influences, by supposing that the sudden physical or 

 mental shock produces an abrupt contraction of the vascular system 

 and, coincidentally, of the uterus ; so that the foetal membranes are 

 thus all at once constricted and slightly lacerated. Consequently, a 

 part of the liquor amnii escapes (as has been frequently observed), and 

 this is succeeded by adhesion of the margin of the laceration in the 

 membranes to the corresponding part of the body of the embryo ; 

 thus are formed those layers or bands which, whether temporary or 

 permanent, disturb more or less the development of the young creature, 

 either by preventing organs from occupying their natural cavities, 

 hindering the union or fusion of parts, or opposing or delaying the 

 formation of those which should afterwards appear. That this opinion 

 is not improbable may be at once conceded, when we remember that 

 during the early stages of development the ovum is little more than a 

 semi-fluid mass, and that its constituent parts are extremely impres- 

 sionable. 



But the formation of monstrosities is more particularly due to what 

 has been designated the theory of retardation or arrested develojmient ; the 

 deviations from the normal standard being the effect of disturbance and 

 arrested supply of nutriment during the period of intra-uterine growth. 

 G. Saint-Hilaire has proved experimentally, by means of eggs artificially 

 hatched, that the production of monstrosities is due to the interruption 

 or accidental suspension of development which had commenced in a 

 regular manner ; while Meckel has shown the striking analogy there 

 exists between many anomalies and various transitory conditions of 

 embryonic organization. 



It has been well remarked that the majority of the malformations 

 due to defect in the higher animals represent, in a more or less perfect 

 manner, the normal conformation of the inferior classes. For instance, 

 the imperfection or absence of limbs is the natural condition of fishes 

 and some reptiles ; the heart is not present in zoophytes ; when it has 

 but one cavity in the higher mammalia, it only resembles the single 

 heart of crustaceae; and when the auricular septum of the heart remains 

 patent, it is like the reptilian heart. All this is explained by the fact 

 that the embryo of the domesticated animals, in arriving at its ultimate 

 development, appears to pass through all the degrees of organization 

 which mark the different types in the zoological series. And by means 

 of the knowledge we possess of the organization of these types, we are 

 sometimes able to say when a particular monstrosity began to deviate 

 from the normal condition, the nature of the deviation, and its cause. 



An excess of general development is less frequent than the opposite 



