106 



METAZOA IN GENERAL 



The organs of the nervous system are the brain and spinal cord, nerves, 

 and various sense organs. Nerves possess sheaths of connective tissue in 

 addition to nervous tissue and are also supplied with blood vessels and 

 smaller nerves. 



Of the reproductive system, the most important organs are the gonads, 

 under which are included the testis of the male and the ovary of the 

 female. There are also to be added the ducts which convey the sperm 



Blood 

 vessel 



Blood 

 vessel 



Nerve 



Articular Ml, 

 cartilage^ 



Fibrous 

 capsule 

 of Joint 



Bone 



Periosteum 



Muscle 

 fibers 



Tendon 



Nerve 



Marrow 



Fig. 43. — A diagram to indicate the nature of bones and muscles as organs and the 

 mode of attachment of a muscle to a bone. A bone as an organ consists of several tissues, 

 such as bone, articular cartilage, marrow, and the fibrous periosteum, and into it enter 

 blood vessels and nerves. A muscle contains muscle fibers, is covered with a fibrous sheath, 

 ends in a tendon, and also is supplied with blood vessels and nerves. The fibers of the ten- 

 don are interwoven with those of the periosteum, from which other fibers penetrate the 

 bone, giving a firmer anchorage. 



cells and egg cells and a variety of other organs, such as yolk glands and 

 shell glands in the female and copulatory organs in the male. 



These organs and systems will be described in greater detail when the 

 animals which possess them are considered. 



128. Other Parts of the Body. — Many divisions of the body are 

 recognized which have no relation to organs and systems, such as the 

 head, neck, trunk, and appendages. Appendages are usually not 

 individual organs but often contain many organs belonging to several 

 different systems. For instance the vertebrate hmb contains organs of 

 the tegumentary, circulatory, skeletal, muscular, and nervous systems. 



