DISSECTION OF THE DOG 193 



membrane, the capsule (capsula lentis). much thicker over the anterior than 

 over the posterior surface. 



If a fresh lens be crushed between the fingers, the peripheral part will 

 be found to be much softer than the more central part. A hardened lens 

 also should be broken by pressure, in order to demonstrate the concentric 

 disposition of laminae of fibres which compose it. 



Camera oculi. — Between the cornea in front and the iris and central 

 part of the lens behind is the anterior chamber of the eye (camera oculi anterior). 

 Within the angle formed by the cornea and iris, the angulus iridis, the aqueous 

 humour finds its way into the spaces of Fontana (spatia anguli iridis [Fontanae]). 

 The posterior chamber of the eye (camera oculi posterior) is a circular interval 

 bounded by the iris, the peripheral part of the anterior surface of the lens, and 

 the projection produced by the anterior extremities of the ciliary processes. 



Dissection. — Remove all the muscles, etc., from about the joint between 

 the mandible and the temporal bone on that side of the head which is 

 yet more or less intact. 



Articulatio mandibulars . — The mandibular articulation occurs between 

 the mandibular fossa of the temporal bone and the condyloid process of the 

 mandible. The two bony surfaces, however, are not in contact, for between 

 them is an articular disc of cartilage (discus articularis) moulded upon the bony 

 articular areas. 



The joint is enclosed by a capsule (capsula articularis) attached around 

 the articular surfaces of the two bones and also to the circumference of the 

 articular disc. Thus it comes to pass that there are in reahty two joint-cavities : 

 one between the temporal bone and the disc, the other between the disc and 

 the condyloid process of the mandible. Each cavity has its own synovial 

 membrane. In general the capsule is strong, but the presence of the temporo- 

 mandibular ligament (lig. temporo-mandibulare) makes it especially so laterally. 



From the conformation of the bony surfaces, the only movements possible 

 in the joint are such as result in depression and elevation of the mandible. 



Dissection. — As a preliminary to the removal of the brain, the remains of 

 the muscles, etc., should be cleared away from the cranial bones. That 

 part of the mandible which is still in position should also be taken away, 

 as well as the zygomatic arch of that side. The cranial bones must now 

 be cut away piecemeal with the bone forceps down to the level of the 

 zygomatic arch. This must be done very cautiously, in order that the 

 fibrous membrane covering the brain, the dura mater, may escape injury. 

 It will be observed that the dura is closely applied to the inner surface of 



