lo March, 1909.] Elements of Animal Physiology. 14: 



THE ELEMENTS OF ANIMAL PHFSIOL OGY. 



W. A. Osborne, M.B., D.Sc, Professor of Physiology and Histology, 

 Dean of the Faculty of Agriculture in the University of Melbourne. 



(Continued from page 85.) 



XVIII. -The Ductless Glands. 



So far as our present knowledge is concerned ihe most unsatisfactory 

 chapter in physiology is that dealing with those organs which have been 

 termed the ductless glands. As the name implies these structures are 

 devoid of any visible efferent channel carrying a secretion. In the case 

 of some of them it is indeed doubtful if any secretion is formed at all, 

 in which case the term " gland " is wrongly used. As regards the 

 functions of the ductless glands we know next to nothing. That the\ 

 play a most important part in the economy of the bod\ has been proved 

 beyond doubt b\- pathological evidence and in the case of some of them 

 by the disastrous results that follow their removal. 



LYMPHATIC GLANDS. — In the chapter on the circulation it was 

 shown that the living cells of the body are bathed in lymph, which fluid 

 can be regarded as a filtrate that has oozed through the thin walls of 

 the blood capillaries. Tlie spaces between the body cells are filled with 

 lymph and these spaces open into minute vessels, the lymphatic capil- 

 laries, which convev the lymph into larger lymphatic vessels and so on 

 until the whole lymph stream is discharged back again into the blood. 

 The flow of lymph is very sluggish and, in the case of the limbs, is 

 practically absent unless the limb be moved or massaged, in which case 

 the lymph is worked along the vessels owing to the rich supply of valves 

 with which these are supplied. But before the lymph is allowed to 

 re-enter the blood it is obliged to pass through at least one lymphatic 

 gland. The lymphatic glands are masses of lymphoid or adenoid tissue, 

 a structure composed of a very open frame- work loaded with round white 

 cells which are remarkably like some of the white cells of the blood. 

 The Ij'mphatic vessel as it enters the gland breaks up into a number of 

 finer vessels and the lymph thereby is brought into intimate contact with 

 the cells of the gland. It is highlv probable that here we have a pro- 

 tective mechanism bv which toxins, or the bacteria themselves, are de- 

 stro3'ed. If, for instance, inflammation occurs in a limb the lymphatic 

 glands (such as those in the human groin), through which the Ivmph 

 draining the infected area passes, swell up and become painful. If 

 the toxins be in excessive amount they mav be able to run the gauntlet 

 of the glands successfully and so enter the circulation producing profound 

 constitutional disturbances. Malignant tumours are verv liable to spread 

 along the lymphatic vessels and infect the glands often fairlv remote 

 from the original seat of mischief. 



In the alimentary canal we find masses of Ivmphoid tissue placed 

 superficially in the mucous membrane. These belong to a slighth dif- 

 ferent category from the lymphatic glands proper because they are not 

 situated in the course of a Ivmph stream ; but the tissue of which thev 

 are composed is practicallv identical with that in the Ivmphatic glands. 

 At the back of the mouth on each side and guarding the entrance to 

 the pharynx we have the tonsils and m the upper part of the pharvnx 

 itself a ring of lymphoid tissue is found which, when swollen, constitutes 

 the well known adenoids. In the small intestine vhe Ivmphoid masses 



