274 PHYSIOLOGY CHAP. 



use of the method of artificial circulation in estimating the 

 results produced in the spinal centres of batrachians by salt 

 solutions at different concentrations. He found that the solution 

 best adapted to maintain the functions of the spinal centres was 

 one containing from 0'6 to 1 per cent sodium chloride. Hypertonic 

 solutions, which contain more than 1-5 per cent sodium chloride, 

 cause motor paralysis after a brief period of motor excitation 

 (tetanus, clonic spasms), while hypotonic solutions, which 

 contain less than 0'6 per cent sodium chloride, cause depression 

 and loss of excitability, but less rapidly and without any previous 

 phase of increased excitability. Since liypertonic solutions 

 withdraw water from the nerve-centres, and liypotonic solutions 

 cause excess of fluid or oedema in them, these experiments of 

 Ducceschi show the importance of water for the metabolism of 

 the ganglion cells. 



Morawitz subsequently worked at the same subject with 

 Verworn, and arrived at the following conclusions which confirm 

 and partly extend those of Ducceschi : (a) If distilled water is cir- 

 culated through a strychninised frog, excitability soon disappears 

 altogether, to reappear on circulating a physiological saline 

 solution. (6) Great loss of water from the cord owing to 

 artificial circulation of a hypertonic solution (2-5 per cent sodium 

 chloride) increases the reflex excitability in the frog till it 

 resembles strychnine poisoning, (c) If more water is added to 

 that contained in the nerve elements, excitability diminishes. 

 Everything therefore tends to show that the excitability of the 

 ganglion cells depends to a large extent on their water content. 



Battelli extended Ducceschi's experiments to the artificial 

 circulation of warm-blooded animals (guinea-pigs) in order to 

 study the influence of water, of certain inorganic salts, and of 

 glucose upon the nutrition, and therewith the excitability of the 

 nerve-centres. 



The following seem to us to be among the most important 

 of his results : (a) Artificial circulation of a deoxygenated salt 

 solution prolongs to some extent the duration of reflex excitability, 

 which only lasts 70 sees, after tying the aorta. (5) A physiological 

 solution saturated with oxygen increases the duration of the 

 reflexes for a variable but not very prolonged period, (c) A 

 mixture of sodium chloride and calcium chloride solution saturated 

 with oxygen gives a marked and constant increase in the reflexes. 

 (d) Potassium and magnesium salts, neutral sulphates and 

 phosphates are tolerated by the centres, but do not increase the 

 duration of the reflexes. () If the artificially circulated fluid 

 has even a moderately alkaline reaction due to the carbonate, 

 bicarbonate, or phosphate of sodium, the vitality of the centres is 

 rapidly abolished. (/) A deoxygenated solution of sodium or 

 calcium causes only a slight prolongation of the functions of the 



