852 GENERATION. 



ti, of the otoliths, and of various . other structures in the auditory apparatus. Sounds 

 may be conducted to the auditory nerves through the bones of the head and the Eus- 

 tachian tube, as is shown by the simple and familiar experiment of placing a tuning-fork 

 in vibration in contact with the head or between the teeth. 



CHAPTER XXVI. 



ORGANS AND ELEMENTS OF GENERATION. 



General considerations Sexual generation Spontaneous generation (so called) Female organs of generation Gen- 

 eral arrangement of the female organs External and internal organs The ovaries Development of the Graa- 

 fian follicles The parovarium The uterus The Fallopian tubes Structure of the ovum Vitelline membrane 

 Yitellus Germinal vesicle and germinal spot Discharge of the ovum Puberty and menstruation Descrip- 

 tion of a menstrual period Characters of the menstrual flow Changes in the uterine mucous membrane during 

 menstruation Changes in the Graaflan follicle after its rupture (corpus luteum) The testicles Tunica vagi- 

 nalis Tunica albuginea Tunica vasculosa Seminiferous tubes Epididymis Vas deferens Vesiculse seminales 



Prostate Glands of the urethra Semen Secretions mixed with the products of the testicles Spermatozoids 



Development of the spermatozoids Seminal fluid in advanced age. 



A EEVIEW of the physiological processes which we have thus far studied shows that 

 the functions of the perfected organism are divided into two great classes: 



The first class of functions may be grouped under the general head of nutrition, 

 taken in its widest sense. Nutrition is common to animal and vegetable life, and this is 

 sometimes called a vegetative process. 



The study of nutrition involves the following considerations : First, the blood, which 

 is the great nutritive fluid, contained in the innumerable vessels which penetrate nearly 

 all of the tissues and organs of the body and are connected with the system of lymphatic 

 and lacteal vessels. Second, the process by which the blood is circulated, sent by the 

 heart to all parts in the capillary system, used by the tissues for their nutrition, then los- 

 ing oxygen, gaining carbonic acid, and being returned by the veins. Third, respiration, 

 the blood being freed from carbonic acid and getting a new supply of oxygen in the 

 lungs, by which it is rendered capable of again circulating through the general system. 

 Fourth, as the blood, in its passage through the capillary vessels, not only loses oxygen, 

 but is more or less impoverished by the assimilation of its nutritive constituents by the 

 tissues, it is necessary to keep it up to the proper nutritive standard ; and this is effected 

 by alimentation, digestion, and absorption. Fifth, we have certain secretions, necessary 

 to the above-mentioned processes ; and the products of physiological waste or decay of 

 the tissues are removed by excretion. Sixth, the processes of vegetative life involve the 

 production of heat and are regulated and coordinated by the nervous system. 



The second class of functions relates to animal life, and these are called the functions 

 of relation. In this class, are included movements, voice and speech, the functions of 

 the cerebro-spinal nervous system, and the operation of the special senses. 



In studying the processes of nutrition of the general system, we observe that certain 

 constituents of the organism, which contain nitrogen and are exclusively of organic ori- 

 gin, have the property, in the living body, of self-regeneration ; i. e., when these parts 

 are brought in contact with nutritive matter in proper form, as it exists in the blood, 

 this matter is appropriated and transformed into the substance of each tissue and organ. 

 It is in this way that, during adult life, the different parts of the organism are maintained 

 in a tolerably uniform condition. In the absence of an exact knowledge of the cause 

 and nature of these assimilative processes, we call them vital ; which term is applied to 

 a constant property of living, organized parts. Physiologists have ascertained that each 

 tissue and organ of the body possesses one or more characteristic organic nitrogenized 

 constituents which are possessed of this so-called vital property. But, at the same time, 



