100 I'UOCKKDINlis OF TMK ANATOMICAL AND AN THKOl'OUXJICA I. 



The heads from which the sections have been made were pre- 

 viously hardened in a solution of formalin, subsequently frozen, and 

 thereafter cut with a saw whose teeth made a rent of i.th of an inch 

 as they passed to and fro. 



A considerable amount of tissue consequently went as debris, 

 and was on this account inevitably lost. The vacancy thus caused 

 accounts for the apparent discrepancy between the appearances pre- 

 sented by the opposing surfaces of sections illustrated in certain of 

 the plates. 



A detailed description of the various structures exposed to view 

 in the individual reproductions seems unnecessary, for the key placed 

 over each plate with leading lines to the prominent landmarks more 

 or less takes such a place. 



I have to thank my senior assistant, Mr. Alexander Low, M.B., 

 for the help which he gave in the whole matter, and Messrs. Andre 

 & Sleigh, Limited, for the care which they bestowed in reproducing 

 the photographs which were submitted to them. 



EECOKD OF ANATOMICAL VAEIATIONS. 



Date of observation, December, 190:5. 

 Sex, Male. 



Abnormal atlas vertebra. 



In this case there is on the left side an arched spiculum, coming 

 out from the superior articular process and curving backwards, but 

 not reaching to the posterior arch. The spiculum is about ^ inch long 

 and } inch broad, and is quite hard and firmly attached to the bone. 

 On the right side there is a small oval mass of bone, which lias evi- 

 dently been developed from a separate centre of ossification. It is 

 attached by ligamentous fibres to the back of the superior articular 

 process, and is smaller and more cancellous in structure than the 

 process on the left side. 



(Signature of observer) NORMAN S. GIWHRIST. 



