CHAPTER XI 

 SECRETION 



Classification of the secretions Mechanism of the production of the true secretions Mechan- 

 ism of the production of the excretions Influence of the composition and pressure of the 

 blood on secretion Influence of the nervous system on secretion Paralytic secretion by 

 glands Anatomical classification of glandular organs Secreting membranes Follicular 

 glands Tubular glands Racemose glands, simple and compound Ductless, or blood- 

 glands Secretions and excretions Synovial membranes and synovia Mucous mem- 

 branes and mucus Mechanism of the secretion of mucus Composition and varieties of 

 mucus General uses of mucus Physiological anatomy of the sebaceous, ceruminous 

 and Meibomian glands Ordinary sebaceous matter Smegma of the prepuce and labia 

 minora Vernix caseosa Cerumen Mammary secretion Mechanism of the secre- 

 tion of milk General conditions which modify the lacteal secretion Properties and 

 composition of milk Microscopical characters of milk Composition of the milk 

 Colostrum Lacteal secretion in the newly born. 



IN the sense in which the term secretion usually is received, it em- 

 braces most of the processes in which there is a separation of matters 

 from the blood or lymph by glandular organs or a formation, by such, 

 organs, of new liquids, out of materials furnished by the blood or lymph. 

 It is probable, however, that most of the secretions are derived directly 

 from the blood and not from the lymph contained in the glandular sub- 

 stance. While secretion may be treated of as a distinct process, it is 

 intimately connected with general metabolism. As a rule, secretions 

 are homogeneous liquids without formed anatomical elements, except 

 as accidental constituents, such as desquamated epithelium in mucus or 

 in sebaceous matter. The secretions are either discharged from the 

 body, when they are called excretions, or, after having performed their 

 proper office as secretions, are absorbed in a more or less modified form. 

 Secretions, therefore, are liquids holding certain substances in solution 

 and sometimes containing peculiar ferments but not necessarily pos- 

 sessing formed anatomical elements separated from the blood or 

 formed by special organs out of materials furnished by the blood. 

 Secreting parts may be membranes, follicles, collections of follicles, 

 or tubes. In the latter instances they are called glands. This defini- 

 tion includes the excretions. It is not strictly correct to speak of 

 formed anatomical elements as products of secretion, except in the 

 instance of fatty particles in milk. The leucocytes found in pus, the 

 spermatozoids of the seminal fluid, and the ovum, which are sometimes 



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