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Mr. D. T. Harris. 



as to allow of the collection of samples of blood from the lingual vein while 

 permitting the normal flow in the interval. No anti-coagulant was used, 

 hut all tubes and cannula? were paraffined. The rate of flow was noted by a 

 drop recorder. 



For the estimation of lactic acid, 20 c.c. of blood was collected directly 

 into 05 per cent. KH 2 P0 4 ; for the determination of the Ph and alkali 

 reserve, the blood was collected under paraffin, oxalate being used as an anti- 

 coagulant. By attaching the hyoid bone to an isometric muscle-lever, the 

 tongue muscles could be made to work against a resistance and develop a 

 measurable tension {e.g., fig. 5). 



Plethysmograph of the tongue : The changes in volume of a curarised tongue 

 were originally studied by Anrep (senior) and Cybulski (1884), and later 

 with the same methods by Piotrowski (1893). For the purposes of the 

 present investigation curarisation could not be adopted for maintaining the 

 tongue, or rather part of it, placidly in the plethysmograph. In order to 

 permit the normal production of metabolites, a technique had to be devised 

 which enabled one to take reliable records of an active muscular organ. 

 Many failures were encountered before the following arrangement was arrived 

 at of accommodating the whole tongue in the plethysmograph and preventing 

 its moving in and out during contraction. 



The genio-hyoid muscles were detached from the symphysis of the jaw and 

 the mucous membrane of the floor of the mouth was cut through in close 

 contact with the alveolar margin as far back as the anterior pillars of the 

 fauces. The tongue was now drawn out ventralwards, all bleeding arrested 

 by ligature and cautery, and the cut edges of the mucous membrane 

 sewn together round the genio-hyoid muscles, carefully avoiding pressure on 

 the lingual vessels and nerves ; the whole tongue could thus be placed in 

 the plethysmograph. To prevent traction on the root of the tongue from 

 without, a tracheal canula was inserted, the trachea being completely cut 

 across ; all muscles coming up to the hyoid were cut between ligatures, and 

 all branches of XII, other than those to the tongue, were severed ; finally> 

 to completely immobilise the larynx and hyoid, a steel rod placed through 

 the mouth into the larynx, and emerging from the upper end of the 

 transected trachea, was firmly clamped to the same stand as the 

 plethysmograph. 



A plethysmograph of circular cross-section was selected which just fitted 

 the tongue ; it was fitted with a cuff of membrane rendered air-tight, yet 

 soft, by means of vaseline. When adjusted it was covered with cotton- 

 wool and connected to a piston recorder : time was allowed for temperature 

 adjustment. 



