NERVOUS SYSTEM. 59 



communicates with a muscle, in a living animal, the 

 muscle is paralyzed. 



Some muscles, as those of the limbs, obey the will of 

 the animal ; others, as those of respiration, may obey the 

 will, but they also act independently of it ; and there are 

 others, as the heart and stomach, over which the will has 

 no control. 



Those muscles which are wholly independent of the will 

 receive their influence from the ganglionic system, de- 

 scribed on page 60. 



As regards the reproductive system of the Mammalia, 

 it is the most perfect in the Animal Kingdom, as already 

 remarked. And, although in some respects * the Mamma- 

 lia agree with Birds and Reptiles in their development 

 from the embryo, it may be stated here, that the relation 

 of parent and offspring in this class is more intimate than 

 in any other class of animals. 



The Nervous system of the Mammals is more highly de- 

 veloped than that of any other animals. It is composed 

 of two parts the nervous system of animal life or cerebro- 

 spinal system, and the ganglionic or nervous system of 

 organic life. 



The Cerebro-spinal system is composed of the cerebrum, 

 cerebellum, and spinal cord, and their branches, as seen in 

 Fig. 25. The nerves of this system extend to the muscles, 

 organs of the special senses, etc. A vertical section of the 



* The Mammalia, Aves (Birds), and Reptilia, agree in having, in their de- 

 velopment from the embryo, an amnion (innermost foetal envelope), and an 

 allantois (a second foetal envelope), and hence are often called the ALLAN- 

 TOIDEA ; and as they are not provided with gills at any period of their ex- 

 istence they are also called ABRANCHIATE VERTEBRATA. 



While Batrachia and Pisces have neither amuion nor allantois (or only a 

 rudimentary one), are often called the ANALLANTOIDEA ; and as they have 

 either permanent gills, or gills at some stage of their existence they are 

 often called the BRANCHIATE VERTEBRATA. 



