230 



On the Rhythmic Contractility of the Spleen. [Jan. 30, 



conclusion which Roy arrived at, that the spleen is practically cut off 

 from the arterial system, and that its circulation is maintained by 

 its own contractions, is thus shown to be incorrect. 



The rhythmic contractions are independent of the central nervous 

 system, for they will proceed after all the nerves passing to the organ 

 are severed, and they can also be shown in an excised spleen perfused 

 with defibrinated arterial blood. 



They are excited to increased activity by intravenous injection of 

 certain drugs and animal extracts which act specifically upon the 

 organ. Prominent amongst these are curare, water extract of supra- 

 renal, and water extract of brain. Suprarenal extract causes an 

 enormous contraction, followed by increased extent of rhythmic 

 waves ; curare and brain extract, mainly the latter, without a prelimi- 

 nary contraction. Indifferent fluids, such as normal salt solution, pro- 

 duce in moderate quantity no such effects (contrary to Roy), and the 

 same is the case with many animal extracts. 



As was shown by Roy, a condition of dyspnoea causes marked con- 

 traction of the spleen. The authors show that this contraction is of 

 central origin, for after severance of all nerves to the organ it is 

 replaced by a passive dilatation, due to the rise of general blood 

 pressure, this being soon followed by an increase in extent of the 

 rhythmic contractions. Temporary cessation of the blood flow through 

 the organ also has the effect of increasing their extent, probably because 

 the splenic tissue is thereby deprived of oxygen and rendered tempo- 

 rarily more excitable. 



The splanchnics, both right and left, contain not only nerve fibres 

 which produce contraction of the spleen (Tarchanoff, Pjluger's Archiv, 

 vol.8; Roy, loc. cit.), but also others which cause dilatation of the 

 organ. 



There is no evidence that the vagi contain any centrifugal fibres 

 which influence the volume of the spleen (contrary to Roy). Provided 

 their inhibitory action upon the heart is neutralised by atropine, even 

 the strongest stimulation of the peripheral end of either cut vagus 

 produces no direct effect upon the spleen. 



Stimulation of any of the nerve-twigs which accompany the arterial 

 branches to the spleen causes strong contraction of the whole organ. 

 The contractions which result from splanchnic stimulation are also 

 obtained even when there is only a minute twig left, all other nerves 

 being severed. There is, therefore, probably a very free nervous com- 

 munication within the organ. 



Evidence has been obtained of the existence of numerous afferent 

 (sensory) fibres in the nerves supplying the spleen. 



