418 J\MES CKAWFORD WATT 



ment occurred which produced the monstrosity of the Umbs, Is 

 it not very probable that the chondrification process in these two 

 abnormal vertebrae was hindered so that the perichordal sep- 

 tum was not broken down, but remained intact, thus producing 

 a vertebra with a divided body? 



Ossification as mentioned above tends to occur in the body 

 from one center, which may be divided. Under such condi- 

 tions, with the perichordal septum intact it is possible that niore 

 of the ossifying center should be in one half than the other, thus 

 accounting for the unequal rate of growth in the two separated 

 halves. 



There are some other points of interest in the vertebral col- 

 umn. The lateral masses of the sacral vertebrae ossify as fol- 

 lows: the first at the fifth month of intrauterine Ufe, the second 

 at the sixth month, the third at the seventh month, the fourth 

 and fifth after birth about three months. In this foetus, the 

 age was given as seven months and the third lateral mass center 

 is just appearing, thus showing a normal rate of growth. 



The first coccygeal vertebra in this foetus has a center of ossi- 

 fication in its body, while normally it appears in the first year 

 after birth, so in this region there is an actual acceleration of 

 ossification, in direct opposition to the retardation or suppression 

 shown in the abnormal portions of the skeleton. 



The core of the limbs at the third week is. filled with vascular 

 mesenchyme which at the fourth week becomes a scleroblas- 

 temal condensation which then becomes successively chondrified 

 and ossified. The primary failure of the digits and ulna of this 

 foetus can thus be placed as far back at least as the fourth or 

 fifth week of development, at the time when the differentiation 

 of the skeletal parts should have occurred. This would corre- 

 spond with the time of production of the defect in the abnormal 

 vertebrae. These facts would seem to indicate that at this par- 

 ticular period was exerted the strongest and most active influ- 

 ence of the agent producing the deformities. 



• Absence of the ulna is a much rarer condition in the forearm 

 than absence of the radius. Kiimmel ('95) has collected a series 

 of cases of defect in the bones of the forearm. Unfortunately 



