95 



X. — Anatomical Notes. — By Professor Hyrtl, of the University 



of Vienna. 



(Continued from Nat. Hist. Rev. for 1861, p. 324.) 

 5. Pneumatic Processes of the Occipital Pone. 



Some time since I directed the attention of anatomists to a very 

 interesting and anomalous process of the condyloid portion of the 

 occipital bone (Wiener. Medic. AVochenschrift, 1860, N. 45). 



This process is sitviated between the articular process of the 

 occipital bone and the mastoid process of the temporal. It pre- 

 sents an elliptical form, the long axis of which is vertical, and its 

 circumference is about that of the tip of one of the fingers. The 

 process is not solid, but consists of many cells, which are in direct 

 comminiication with the " air-containing" cells of the mastoid pro- 

 cess. Hence I have called these processes " Pnemnatic." 



Since the notice above referred to was written, two additional 

 instances of the occurrence of this process have presented themselves 

 to me. One was given me by a student, who found the skull in a 

 large bonehouse in a burying place, in his native town in Bohemia. 

 The other was observed in a female skull, from my dissecting room. 

 In both of them the processes are as large as a hazel-nut, and they 

 are covered by so thin a- layer of compact osseous structure, that the 

 internal arrangement of the air-containing cells can be easily dis- 

 tinguished. In the female skull refen-ed to, the cells of the pneu- 

 matic process extend as far as the condyloid process of the occipital 

 bone, where they lose their partition walls and unite to form a single 

 rather large cavity. 



It is a curious fact, that the cells of the pneumatic process commu- 

 nicate with those of the mastoid, passing, as they do, across the mastoid 

 suture ; but there are many similar cases in Comparative Anatomy, 

 where the pneumatic cavity of the frontal bone extends (across the 

 coronal and lamhdoid suture) to the occipital bone {Elej^lias and 

 almost all other Pachydermata). 



These pneumatic processes have been since observed by several of 

 my fellow-anatomists, who have, in sundiy communications to me, 

 confirmed my observations in this matter; and I doubt not but 

 that every Craniological Collection of any extent will likewise afford 

 evidence of their existence. 



I can boast of the possession of a very large series of crania, as 

 for a long time past all the skulls of the subjects of my dissecting 

 rooms are carefully prepared by maceration, and the number so pre- 

 pared varies each year from 200 to 300, yielding thus an abundant 

 supply for the hunting out of anatomical curiosities. 



A careful investigator will not confound the new process with the 

 paramastoid process, which is very often present in skulls. This 

 latter is a strong process, with a thick layer of compact substance, 



