THE NERVOUS SYSTEM. 35 



ever, should, when thus employee], only bo taken in connection with other an- 

 atomical characters. 



In the brachium we find, as a rule, a well developed f/icej)s, the deltoid, 

 triceps, and the hrachialis anticus, while the muscles of the forearm and hand, 

 over a dozen in number, are interesting to study, especially in the light of their 

 subservience to the power of flight. About thirty muscles make up the mus- 

 culature of the lower or pelvic extremity of a passerine bird. A mrtorius ex- 

 ists, and a group of three gluteal muscles, with U\u V(isfi,abicej)s Jlcxoi' cruris, 

 and a group that have been extensively used in classification, namely, the semi- 

 tcndinosus, the accessory seniitendinosus, semimemhranosim, axid femm'o-caudal. 

 The amhiois, a muscle about which so much has been written and said, does 

 not occur in a itaven. The group of extensors &xiA flexors are very perfect, con- 

 trolling many of the movements of the leg and the toes. The soleus and the 

 gemellus are also present. One of the flexors, in connection with the amhievs, 

 the_/. d. jH'rforatus, by its semimochanical, automatic, and to some extent its 

 involuntary action, controls the grasping power of the toes in some perching 

 birds, so when squatting down on their roosts asleep, the feet, without sus- 

 tained effort, seizes the perch and thus prevents the bird from falling or toppling 

 over. The amhlens being absent in the Passercs, this function depends on 

 the action of i\iQ flexors alone. 



A long list of special muscles are to be found in the neck, and others in 

 the trunk, associated with expiration and inspiration. Several abdominal 

 muscles also exist, and a rudimentary diaphragm is frequently present, best 

 developed in the Apteryx. Some seven (7) pairs of muscles control the move- 

 ments of the tail in the Raven, and their action offers a very interesting chapter 

 in mechanical physiology. 



THE BEAIN AND THE REST OF THE NERVOUS SYSTEM. 



In Birds, the JVcrvoiis System, in common with that of reptiles, exhibits 

 considerable advance in specialization above what we find in the lower verte- 

 brates. As in other great groups, it consists of the spinal cord and brain, 

 composing the central portion, and the cranial and spinal nerves, including 

 the sympathetic system, all of which latter represent a peripheral portion. Upon 

 examining it in the Raven and in other birds we find that the brain completely 

 fills the cavity of the cranial casket; the hemispheres of the cerebrum are large and 

 smooth, and these taken in connection with the thalamencephalon constitute 

 \he forebrain in a bird. There are also a hind and a mid brain, the former 

 being composed of the medulla oblongata, and the latter of the cortex of the 

 optic lobes and the peduncles of the fore-brain. The pineal body rises to the 

 surface between the hemispheres and the cerebellum, and the optic thalami 



