456 DR HARRY RAINY AND DR J. W. BALLANTYNE. 



which, whether it is eventually found to be true or not, will at least help us to 

 arrive at a clearer conception of their production. 



The examples whose skiagrams form the subject of this communication may be 

 arranged, in accordance with the suggested classification, into : (A) cases where a 

 complete system of " determinants " is absent ; of this group achondroplasia may 

 serve as a type: (B) cases where parts of one or more systems of "determinants" 

 are absent ; this is exemplified in anencephaly and aprosopia : (C) cases where the 

 " determinants " though apparently present may, in consequence of some inherent 

 defect, lead to anomalous developments ; some instances of iniencephaly may be 

 placed in this group : (D) cases where there is an excess of " determinants," as in 

 Polydactyly and dichirus. 



These various defects in " determinants " are revealed in the soma of the cases that 

 form the subject of this paper, but doubtless the defect is transmitted, at least in some 

 cases, in the germ plasm also, and so may become hereditary, if the somatic deformity 

 is not so serious as to preclude the foetus from attaining to sexual maturity. 



There are many forms of monster which do not find a place in the above scheme, 

 for, even where the character and grouping of the " determinants " are normal, the 

 moulding of the embryo is interfered with by pathological occurrences during intra- 

 uterine existence, and there is but little doubt that the amnion (whose formation in 

 the mammalian embryo is very different from that described in the chick) is fre- 

 quently responsible for grave disturbances of normal development. 



Group A. 

 {Characterised by total absence of a system of determinants.) 



This type is represented by the following cases of achondroplasia. 



The first case is that of a female infant born in the practice of Dr Mowat of 

 Edinburgh in 1903. The external appearance is shown in fig. 1, Plate II, and a 

 frozen section of the body is reproduced in colour in Plate I, fig. a. 



The X-ray photograph (fig. 2, Plate II) shows the characteristic defect in the 

 formation of those bones of the basis cranii which are early prefigured in cartilage, 

 causing marked indentation at the root of the nose. It also demonstrates the extreme 

 shortness of the long bones, and the broadening of the hands. 



The second case is that of a full-time male foetus which also presents a very 

 typical example of the condition. Fig. 3, Plate III, shows the general appearance at 

 birth ; fig. 4 shows the broad, short forearm and hand ; whilst fig. 5 is a stereoscopic 

 photograph of the head, which'enables one to distinguish with great clearness the 

 details of the defective development in the basis cranii. 



Fig. 6, Plate IV, represents the subsequent development of the wrist and hand 

 bones in achondroplasia, as exhibited in an adolescent patient. Fig. 7 shows the final 

 result in an adult case of the same abnormality. 



