On Relationship between Staircase phenomenon and fatigue. 



exposed surface of the meduUa oblongata and their effect 

 upon the respiratory rhythm noted. 



It was found that °/jo Solutions of acids (hydrochloric, 

 sulphuric, lactic, oxalic) caused a notable acceleration. Thus 

 in a frog breathing at the rate of about 19 respirations a 

 minute the application of ^/^^ HgSO^ quickened the rate, within 

 two minutes, to 50 respirations per minute. In other instances 

 less acceleration was obtained, but in all cases it was very 

 marked, except when the respiratory rhythm before the appli- 

 cation of the acid was very convulsive and irregulär in 

 character owing to injury of the meduUa during the Operation ; 

 in these instances it is possible that only the spinal centres 

 were functioning. 



One per cent KCN caused complete stoppage of respiration 

 within three to five minutes. Strong reducings agents (1 percent 

 Formaldehyde, °/jq K S, ^/^^ hydroquinol, '/^ n sulphurous acid) 

 caused marked slowing or stoppage of respiration; the application 

 of hydriquinol was also foUowed by the muscular tremblings 

 and cramps such as were found by Landois and Maxwell 

 to foUow the application of Creatin to the cortex in mammals; 

 Oxidising agents (20% Kahlbaum's C. P. H^Og. «/loKMnO^, 

 ° /lo ^^2^16) accelerated the rhythm, but not markedly. Respi- 

 ration was inhibited by °/j„ CuClg and slowed, but not markedly, 

 by "/loHgClg. Solutions of a much higher osmotic pressure 

 than the blood (e. g. pure glycerol) moderately accelerate the 

 rhythm and render it irregulär; prolonged action of Solution» 

 of a much lower osmotic pressure than the blood (distilled 

 water, tap water) greatly slows the respiratory rhythm and 

 may ultimately suppress it altogether. In confirmation of 

 Maxwell's results I find that Sodium Oxalate and Barium 

 Chloride, both powerful nerve-fibre stimulants, have no noticeable 

 effect upon the rhythm. It may be questioned whether the 

 effects observed are really due to the direct action of the 

 substances upon the respiratory centre or whether they are 

 reflex effects due to the action of the substances upon nerve- 

 fibres, If, however, we cover the lower limbs of the frog, 

 treated as described above, with a sheet of filter-paper saturated 

 with "/j^HCl, after 3 or 4 minutes of violent struggHng the 

 frog becomes quiet and the respirations, at first inhibited, are 



•^♦Wr*^ 



