INHIBITORY NERVES TO THE VASCULAR SYSTEM Si 



in which no striation could be seen. He ascribed the tonic 

 rhythmical contractions to the contractions of this layer. Bottazzi 

 found the two kinds of contraction behaved differently to stimu- 

 lation of the cardiac nerves ; stimulation of the augmentors in- 

 hibits these tonic contractions so that the auricular beats now all 

 start from the same base line, while, of course, the beats are them- 

 selves increased in strength ; conversely stimulation of the vagus 

 will make the tonic rhythm appear, if it is not present, and in- 

 crease the strength of the waves if they are weak, while, as is 

 well known, it diminishes the strength of the auricular beats. 

 Rosenzweig has been unable to confirm these statements of 

 Bottazzi, so far at all events as the vagus is concerned. 



At the same time Bottazzi's statements agree in a remarkable 

 way with Fano's observation upon the action of atropine and 

 muscarine upon these two kinds of rhythm, for atropine is essentially 

 a paralyzer of the activity of muscular structures, to which the 

 vagus cells send motor fibres, while it leaves alone or even in- 

 creases the activity of muscular structures whose motor fibres 

 belong to sympathetic cells ; and muscarine paralyzes the lattei 

 but not the former. 



Since Rosenzweig's paper, Bottazzi has re-examined the 

 question. He finds that it is not necessary to use a clamp or to 

 bleed the animal, or to wait a long time for the appearance of 

 the tonic rhythm in the auricle, if the animals are cooled down 

 in an ice chest at a temperature of 9 C. This he says is indis- 

 pensable in order to be sure of obtaining auricles with a good 

 tonic rhythm and responsive to nerve stimulation. He confirms 

 his previous observations on the respective actions of the two 

 cardiac nerves, and also shows that adrenaline produces the 

 same effect upon the two rhythms as stimulation of the sympa- 

 thetic. Oinuma has confirmed Bottazzi's observations on thecardiac 

 nerves, and I have seen the same action of adrenaline as he de- 

 scribes upon the auricle of Chrysomis Picta, an American species 

 allied to Emys. Bottazzi also in conjunction with Ganfini has ex- 

 amined histologically the auricular tissue of Emys, and has con- 

 firmed Rosenzweig's discovery of unstriped muscle fibres in the 

 auricle. They form a strong layer next to the endothelium and 

 continue into the sinus venosus and the beginnings of the great 

 veins ; the striated muscle fibres also continue into such a vein as 

 the vena hepatica, always lying external to the layer of unstriped 



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