GRAPHIC OF ARTERIAL PRESSURE 33 



from the cut surface of the spinal cord, and make oiit the grey matter and 

 the lateral white columns. Set the primary circuit running for faradization 

 and open the short-circuit key in the secondary. 



Steadying the neck-stump with one hand, with the other apply the 

 point of the stigmatic electrode to one of the lateral columns for 8-8 sees., 

 while your colleague notes any effect on the arterial-pressure manometer 

 (text-fig. 16). A rise of pressure of somewhat gradual and stepped 

 culmination ensues, which is soon accompanied by quickened pulse-rate ; 

 note the latency of both effects, and the long after-action on withdrawal 

 of stimulus. If no effect results from moderate faradization, shave off a 

 thin slice of the cord with a sharp scalpel and reapply the electrode. 



Note that stimulation of the cross-face of the dorsal columns produces 

 no effect on the blood-pressure, unless the currents be strong when there 

 is escape to the lateral columns. 



X. Stimulation of the cross-face of the dorsal columns does, however, Obs. 21. 



evoke muscular movements ; the movement evoked from the lateral division Antidrome 



. ... conduction in 



{cuneate) is in the ipsilateral forelimb, that from the medial [graciJe] division i^ie spinal 



is in ipsilateral hind-limb ; in both cases the movement is flexion, in cord. 



the hind-limb usually of ankle or knee, in the forelimb of elbow. These 



movements are due to antidrome conduction down the dorsal root-fibres 



composing these columns, collaterals coming off from the cuneatus fibres in 



the brachial region, from the gracilis fibres in the lumbo-sacral. 



ANNOTATION 



Ohs. 16. If it is permissible to regard cedure by using a U-tube containing Hg 



the preceding exercise (exerc. IV) as follow- as manometer and by employing a sodium 



ing Harvey's Exercitatio of 1628, the carbonate solution in the junctional tube to 



present exercise may be regarded as following retard clotting {Becherches sur la force du 



Stephen Hales's Haemastatics of 1737. coeur aortique, Paris). The float riding on 



Hales was the first to measure the pressure the Hg and carrying a pen for writing on 



of the blood, 1737 {Statical Essays, Haema- travelling recording-paper is due to Ludwig 



statics, vol. ii, London). He measured it (1847, Arch. f. Fhysiol.) 

 manometrically by ligating a brass tube to Mean arterial pressure is well given by 



the crural artery of a horse, and connecting the Hg manometer ; but for the details of 



the metal tube with a vertical glass one. such rapid changes of the pressure as the 



He observed that the blood-column rose to pulse the inertia of the Hg columns is too 



a height of 8' 3", with oscillations due to great to give them faithfully. These are 



the heart-beats and ranging between 3" and recorded better by spring resistances such as 



10". Poiseuille improved (1828) the pro- are provided by metal membranes of limited 



