42 MALL. [Vor. XIX. 
marked histolysis of the cord and brain. Similar changes 
can be produced in birds, while in man the number of cases 
of spina bifida and anencephaly are at least ten times as 
numerous in the embryo as in the fcetus. 
In man, however, the pathological changes in the embryo 
are very marked and complicated by an arrest of the develop- 
ment of the heart or by its complete destruction. In my 
specimens no doubt the destruction of the heart must be held 
responsible for the general cedema and the marked histolysis 
of many of the tissues, including those of the brain. It may 
be that the faulty implantation of the ovum affects the heart 
first and that the changes in the nervous system are produced 
secondarily, but our data are too meager to allow us to draw 
any conclusion regarding the sequence of events. At any 
rate, there must be other factors at work which make the 
process more complicated than it would be if there were 
only a simple arrest of the development of the spinal cord. 
The other changes are in the region of the spinal cord and 
canal and aid in producing the various forms of spina bifida, 
including spina bifida occulta, which are found in the fcetus 
and at birth. 
In some instances, in which the individual lives after birth, 
the primary change must have been of a slight degree to begin 
with, and the faulty implantation of the ovum must have been 
corrected, or in case the ovum was poisoned, the disease must 
have been eliminated in order to allow the embryo to continue 
its development. However, very simple or uncomplicated 
cases must be very rare, for spina bifida is usually accom- 
panied with other malformations, as is the case with most 
monsters. 
