■ ( ;i<s() ) 



outside to llic vcii.i (';i\;i, l)iil llial it oriuin.itcs in thai place in a 

 definite j)Ci-i()d. It is cerlaiidv llie most iiatui-al and the most suilaltle 

 expltiiiation of llie phenomenon to assume tiiat at the \'e]iae caA'ae 

 (as is know II to l»e tlie ease in less de,i>,i-ee in the other parts of tlio iieart) 

 contiiiiially stimiilatiiiLi' nialtei- is formed, till this obtains such a 

 strength tliat a contraction is caused. AV'lien howcxer, the muscle 

 fibres contract the stimiilatinu' matter seems to lia\"e heen uscmI np 

 or at least to have heen destroyed, so that every lime after a con- 

 ti'aetion the same time is wanted to jn-odiice new stimnlatinu' matter 

 to such a strenu'th that auain a contraction follows. This destroxinu' 

 of the stimnlatinu' matter (dissociation in Ions, chemical chanu'es 

 or \vhate\-er this may he) always takes place when there is a 

 contraction, w hetluM- the systole» is caused hy the stimnlalinii' matter 

 itself oi* caused Ity a stimulus induced from elsew Ikmh». I^'or it 

 is a well-known fact, that liy artiticial stimnlation of the auricle 

 or the ventricle, moi-e freepient than the spontaneous rhythm, the 

 latter can l)e enlii-ely overpowered. 



Another explanation is that at \\\o vena ca\a tli(M-(> is a continual 

 stimulation constant in streuulh, ex|>ressinu- itself periodically in 

 systoles, hecaiise with each systole irritability, contractility and coii- 

 ductiA'e |)ow(M' of the heart muscle are nentrali/ed : so if a systole 

 has taken place it always auaiii lasts a cei-tain time before the heart 

 has recoNcred itself in so far that another contraction is ))ossible. 

 Enoelmann objects to this, that the explosion broiii-ht about by the 

 contraction in the molecular system of the muscle cell will destroy 

 the stinmlatinu' matter in stock toiicther with the (ttlier properti(>s of 

 this muscle cell, ( irrital>ility , contractility and coiiducti\'e |>ow{'r); 

 moreoNcr (li<l hA(;i'',i,MANN show that the period i»f the f(U-mation of 

 the stimulus can be chanii-ed independent of the irritability in the 

 ^\■all of the N'ena by clironotro|)ic ner\(' influence. So we must 

 assume that tlu^ systole d(>slioys the stimnlalin.u- matter and that 

 e\ery time the latter must auain dexclop itself after ovvvv systole 

 to actixe power. The law of the preserxation of the physiolouical 

 peri(Kl of stimulation dominatinu' the duration of the ccunpensalorv 

 l>ause and all the important data come to light by means of /'the 

 method of the extra-systoles" for the frog's heart have been traced 

 by CusHNV and Mattukws (1) for the mammalian heart. These in- 

 vestigators shoxved that tlu^ mammalian heart obeys the same laxvs 

 as the frog's heart, that its activity is doniinatetl by the same fun- 

 damental prop(M-ties of the til)res of the heart muscle, that the same 

 theories hold good for both. 



Only in one respect they found a difference: x\ hen the auricle is 



