446 PHYSIOLOGY CHAP. 



more exactly in which section of the bulb lesions brought 



about a sudden respiratory standstill. He carefully located the 



site of the bulbar lesions inflicted during the life of the animal, by 



microscopic examination of the hardened and stained preparations. 



He found that the arrest of the respiratory movements was 



invariably determined by the division, or at any rate the injury, of 



'the solitary bundle, which he regarded as the respiratory centre 



' proper, since it consists of a column of small multipolar nerve cells, 



mingled with nerve fibres. 



^ Gierke's results do not contradict those of Schiff, since it is 

 impossible to divide the solitary bundle without at the same time 

 destroying the external, deep section of the dorsal nucleus of the 

 vagus or the nerve fibres descending from it. It is only the 

 interpretation of the results that differs. 



' In 1892 Gad and Marinesco published a series of interesting 

 experiments on the slow and gradual destruction of the floor of 

 the fourth ventricle by the method of repeated punctiform cauterisa- 

 tion by fine glass rods, rounded and heated at the end, which 

 avoided haemorrhage, traction, and pressure on the adjacent parts. 

 By these experiments, undertaken with the utmost precaution, 

 they were able to destroy not only Flourens' nceud vital at the 

 apex of the calamus scriptorius, but also the external portion of 

 the ala cinerea, including the solitary bundle, without finally 

 bringing respiration to a standstill. They frequently noted 

 respiratory disturbances and even arrest, due to excitation of 

 inhibitory paths, which soon passed off, and permitted them to 

 proceed cautiously with the cauterisation. Only when the lesion 



- was prolonged deep into the formatio reticularis was there final 



- arrest of respiration. In addition to the respiratory tracts, 



- descending to the spinal centres, the formatio reticularis contains 

 a number of cells, which, although few in number, and not grouped 

 into a nucleus, may very well as a whole represent the respiratory 

 centre. At the same time it is not necessary to destroy the 

 whole of this formation to obtain immediate arrest of respiration. 



With Deiters, Gad distinguished that part of the formatio 

 reticularis, which lies medially to the root of the hypoglossus and 

 extends to the raphe, from the lateral part which lies outside this 

 root. In rabbit it is only necessary to injure this last segment 

 deeply enough, in order to produce permanent arrest of the 

 respiratory movements. In the cat, on the other hand, the same 

 result is obtained by cauterising the part which lies between the 

 * root of the hypoglossus and the raphe. In any case, whatever 

 segment of the formatio reticularis is destroyed, it suffices, if not 

 to bring about total arrest of the respiration, invariably to produce 

 a considerable weakening in respiratory energy. It is therefore 

 probable that the whole of the formatio reticularis (which as a 

 unit includes a much more extensive segment of the bulb than the 



