496 PHYSIOLOGY CHAP. 



the rabbit. When the section falls at the level of the apex of the 

 alae cinereae, respiration immediately becomes periodical. After 

 long pauses groups of three, four, or five respirations occur, which 

 decrease in depth (Fig. 233). On dividing the medulla at a 

 higher point, periodic respiration may sometimes be observed when 

 pressure is exerted on the respiratory centres by the extravasation 

 of blood in the neighbourhood of the alae cinereae. On removing 

 the clot ordinary respiration is reinstated. Sometimes, after section 

 of the bulb, respiration will at first be normal and subsequently 

 become periodic, perhaps owing to the exposure of the bulb to air. 

 In conclusion no essential difference from the results we pub- 

 lished eight years previously. 



In 1874, on studying the course of asphyxia in narcotised and 

 tracheotomised dogs, with intact or divided vagi, making them 

 breathe into a large closed receiver, which transmitted the respiratory 

 movements to a writing tambour, we not infrequently observed, in 

 the final moments before the death of the animal, the formation 

 of a series of small groups consisting of two respirations, the first 

 being somewhat deeper than the second, separated by pauses 

 occupying a period about three times as great as that of the 

 groups (tracings similar to that of Fig. 231). So that the mode 

 in which the vitality of the respiratory centres dies out in 

 asphyxia recalls the modus moriendi of the frog's heart, when 

 excised and filled with serum that is never regenerated (see 

 Chap. IX. 3). 



In 1880 Sokolow and Luchsinger published their ingenious 

 researches on the respiratory phenomenon observed in the frog, 

 during asphyxia of the centres from ligature of the aorta, and 

 during the resumption of activity when the ligature has been 

 removed. They noticed that in the first case the number of 

 respirations in the successive groups diminishes, while the subse- 

 quent pauses are prolonged ; in the second case the opposite occurs, 

 i.e. the groups become progressively larger and the pauses shorter 

 until normal rhythmical respiration is resumed. We have no 

 information as to the form of the groups, the authors not having 

 employed the graphic method. 



The important researches of Fano, carried out in our laboratory 

 at Florence in 1883, on the periodic respiration of tortoises, 

 agree perfectly with those of Sokolow and Luchsinger, although 

 they grew out of a side issue. After excising the heart of a big 

 land tortoise he saw that the animal continued to breathe, no 

 longer rhythmically, but in groups separated by long pauses. 

 Periodic respiration (though of a highly irregular character in 

 regard to number of respirations and duration of groups and 

 pauses) is very frequently observed, both in land and water 

 tortoises, during the winter lethargy. In the majority of groups 

 the respirations present much the same amplitude, and none of 



