1890 - 91 .] Drs Symington & Thomson on Defective Ossification. 273 
Microscopically the following changes were observed. The acini 
were irregular in size and shape. The blood-vessels remarkably 
distended with blood, and here and there so tortuous, as apparently 
to project into the lumen of the acini. The epithelial cells were of 
large size, roughly cubical in shape, with a large nucleus and relatively 
large amount of protoplasm. In some parts the cells were adherent 
to the walls of the acini, but for the most part were lying loose 
in their interior, almost filling them with desquamated cells, from 
some of which, more granular than the rest, the nucleus had dis- 
appeared. There was no marked leucocyte infiltration. 
“ The changes above described may be included in the term acute 
desquamative catarrh.” 
As the foetus had been dead about eight days when we received 
it, the brain and spinal cord were not sufficiently well preserved for 
microscopic examination, but we succeeded in demonstrating some 
interesting changes in the general configuration of the brain. As 
these, however, were secondary to certain deformities in the cranium, 
we will defer their description until after that of the skull bones. 
The essential and characteristic lesion in this specimen is found in 
connection with the skeleton ; and before proceeding to describe in 
detail the alterations in the individual bones, it appears advisable to 
state first, in general terms, that the alterations present are confined to 
certain groups of bones, while others are quite normal. The latter are — 
(1) Those which are formed entirely in membrane, e.g., the flat 
bones of the vault of the skull. 
(2) Those which, although formed in cartilage, remain entirely 
or mainly cartilaginous till an advanced period of foetal life, 
so that their general growth is quite independent of endo- 
chondral ossification. As examples of these may be mentioned 
the sternum, costal cartilages, patella, and the tarsal and 
carpal bones. 
The departures from the normal affect those parts of the skeleton 
which, formed in cartilage, largely depend for their growth during 
foetal life upon endochondral ossification, the cause of the departure 
being a premature arrest or absence of this process. The bones 
belonging to this group are the long bones of the extremities, the ribs, 
the posterior part of the base of the skull and the innominate bones. 
