98 PROF. HOWES ON SYNOSTOSIS AND [Feb. 6, 



recently deposited in the College of Surgeons' Museum is that of a 

 Sole (of which vertebrae nos. 8 to 21 are unfortunately alone pre- 

 served) in which the co-ossification of the five vertebrae numbering 

 14 to 18 is closely approximate in condition to Hyrtl's first 

 recorded examples. The co-ossified vertebrae (fig. 5) collectively 

 occupy an area of less than two normal vertebra? ; and in corre- 

 lation with the compression which the former have undergone, 

 their related arches, being approximated at their bases, form a 

 series of radiating outgrowths. Except that the 18th neural spine 

 bears a conspicuous synostotic enlargement (sy.), with signs of 

 previous dismemberment, the remaining parts are normal. 



More interesting than this specimen is that numbered 500 in 

 the College of Surgeons' Catalogue (fig. 6). The vertebrae between 

 and including the (ith and the Jibth are in this case preserved, and 

 special interest centres in the 12 postanal, which number 23 

 to 34 inclusive, and are very closely compressed although not 

 co-ossified. 



Except for the co-ossification of the right half of the 14th 

 ha?mal arch with the left half of the loth, and an accompanying 

 absence of the right half of the latter and total independence of 

 the two halves of the former, the remaining vertebrae are in every 

 respect normal ; and as these correspond in detail with their 

 numerical homologues in the normal column, there is little room for 

 the supposition, which might at first present itself, that the com- 

 pressed vertebra? are perhaps intercalary in nature. 



The twelve compressed vertebrae are very dense, and the area 

 which they collectively occupy is equivalent to that of the seven 

 immediately in front of them. As compared with the specimen 

 last described, they are in a much less compressed condition ; and 

 the feeble approximation of their arches amply testifies to this 

 assertion. The most instructive feature of this specimen is the 

 circumferential increase of the bodies of the compressed vertebrae 

 over those of the rest of the column ; and, in adaptation to the 

 conditions imposed, the faces of the vertebrae (nos. 22 and 35) that 

 immediately abut against the compressed series are sympathetically 

 modified. At first sight these compressed vertebra? would appear 

 to be in a condition of retarded growth, and to consist, bulk 

 for bulk, of less osseous matter than a corresponding number 

 of normal ones. When placed in the scale, however, they were 

 found to be the heavier of the two 1 . It is clear from this that 

 mere compression of bony structures over a given bodily area need 

 not necessarily be accompanied by a diminution in bone-forming 

 activity ; and in the case under consideration the surplus material 

 appears to have largely encroached upon the periosteal and inter- 

 vertebral tissues. The arches remained free and did not parti- 

 cipate in the excess. 



The remaining specimen to which I would direct attention is 



1 '660 grin, as compared with "575 for the twelve next in order of succession 

 anteriorly. 



