568 EEPORT— 1882. 



are others which when stimulated occasion, on the contrary, the dilatation of 

 arteries — the so-called ' vaso-inhibitory ' or ' vaso-dilator ' nerves. That it was not 

 stimulation of the vaso-dilator nerves, which, by increasino: the amount and the 

 pressure of the blood flowing through the capillaries, occasioned the secretion of 

 saliva, was shown by several experiments, but especially by an observation of 

 Keuchel. This observer foimd that the alkaloid of the deadh' nightshade, viz. 

 atropia,when introduced into the system, exerts such an action, that on stimulating 

 the chorda tyrapani no secretion of saliva follows ; whilst, on the other hand, 

 dilatation of the arteries is produced exactly as under normal circumstances. 

 Other drugs have since been discovered which exert a similar action to that of 

 atropia in paralysing secretory nerves, whilst some are now known which antago- 

 nise the action of atropia, and restore the suspended activity of the secretory 

 nerves. From these studies has unquestionablj' resulted a knowledge of the con- 

 clusion, that although the process of secretion is favourably influenced by the 

 vascular dilatation which follows the state of aclivity of the vaso-dilator nerves, the 

 actual process of secretion is not due to them, but, so far as it is controlled by the 

 nervous system, is directly under the influence of certain nerves which may be 

 termed secretory. 



Discoveries which show that Seceetion, though influenced by, is not 



NECESSARILY DEPENDENT UrON, STIMULATION OF NeRVES GOING TO A GlAND. 



A knowledge of the facts which I have brought before you hitherto would of 

 itself lead you to suppose that glandular secretion is a process which is in abeyance 

 except under the influence of stimulation of nerves which throw the gland into 

 activity, in the same mnnuer as the quiescent muscle passes into activity normally, 

 only when its motor nerves are stimulated. But this supposition, though it may be' 

 in some measure true in the case of certain glands, is not borne out by a study of 

 secreting glands in general — a study which teaches us that whilst the activity of 

 the gland-cells may be, and often is, remarkably under the control of the nervous 

 system, it is by no means necessarily dependent upon it. The activity of the 

 gland depends upon the activity of its individual units, the gland-cells; and these 

 units may discharge their function so long as they continue to live and are supplied 

 with the nutriment — mineral, organic, and gaseous — which tliejMequire. 



Leaving aside, at least for the present, any reference to the arguments which 

 may be derived, by analogy, from a study of cell life in general, I would call your 

 attention to the physiological facts which prove the truth of the proposition just 

 enunciated. The first of these facts was discovered by Claude Bernard: to wit, that 

 when all the nerves supplying the salivary glands are divided, there is at first a 

 temporary cessation of secretion, soon followed, however, by an abundant flow of 

 very watery, so-called paralytic saliva. 



This result is fully confirmed by similar observations made in the case of other 

 secreting organs, and which establish verj' fully the greater or less independence 

 of the secreting elements from the control of the nervous system ; though unques- 

 tionably, in a normal state of the organism of higher animals, the nervous system is 

 continually intervening, both directly by its influence on gland-cells, and indirectly 

 by the changes which it produces in the circulation, so as to control the operations 

 of gland-cells, and especially to bring them into relation with, and subordinate them 

 to, the work of complex processes of the organism. 



What the exact relations of nerve-fibres to gland-cells may be is yet a matter 

 involved in great doubt. The discovery made by Pfliiger of the terminations of 

 nerve-fibres in the secreting cells of the salivary glands has not been confirmed by 

 any observers in any vertebrate. Kupflfer has, however, unquestionablj^ done so in 

 the case of Blatta orientalis, and although as yet objective proof is wanting, we 

 cannot entertain any reasonable doubts that a connection between the ultimate 

 fibrijlse of nerves and secreting cells actuall}' exists. AVe feel confident that 

 physical, as it were accidental, difficulties have alone hindered the precise deter- 

 mination of the fact. 



