952 



those two forms, i.e., the envelope of one systenn of osculating 

 elli|)ses has 4 cusps, the envelope of the other has none. 



Case 2 is to be considered as a combination of Fig. 9 and Fig. 

 10. a touches (C) in two points, h has two cusps on the line which 

 connects with the points of contact of ^ with (C). The dynamical 

 problem allows of a single sim[)le vibration. 



Case 3 gives rise to a combination of Fig. 10 and Fig. 11 (or 

 Fig. 12). There is one system of osculating ellipses. 



Case 4 to a combination of Fig. 10 and Fig. 11 (or Fig. 12). 

 There is one system of osculating ellipses. Moreover the dynamical 

 problem allows of a simple vil)ration. 



In the Cc\se p <^ we have again in the first place envelopes 

 corresponding in the main with those represented in the Fig. 14— 20. 

 We should, however, bear in mind, that in general the cusps do 

 not disappear by 8 but by 4 at a time. There is for instance a 

 transitional form possible between Fig. 18 and Fig. 19 in which 4 

 cusps occur, and in Fig. 14 and Fig. 15 4 cusps may have fallen 

 out. In order to obtain Ihe other forms of the envelope we must 

 make use of the observation al)ont (/>') in § 7. 



If the branch of yL) lying outside (C) touches (6') in two points, 

 then the dynamical problem allows of o?ie simple vibration. If {L) 

 cuts (C) in 4 points, then we get one of the two domains of motion 

 of Fig. 16, etc. 



Is (K) an hyperbola or a degeneration then the various shapes of 

 (L) may be deduced in the same way from tlie Fig. 3 — 0. 



Physiology. — "On the rejiectorical influence of the thoracal auto- 

 nomical nervou.^ system on the rigor mortis in cold-hlooded 

 animals." '). B_\ S. dk BotR. (Communicated by Prof. C. A. 

 Pekelharing.) 



(Communicated in tlie meeting of Januai-y 31, 1914). 



The rigor mortis that is caused by hardening and shortening of 

 the muscles begins in warm- and cold-blooded animals after the 

 circulation of the blood has stopped for some time, in warm-blooded 

 ones 5—8 hours, in cold-blooded ones 1 — 2 days. If with a muscle 

 that has been removed, we make provision for a sufficient supply 

 of oxygen, it mortifies without stiffening. A special chemical state 



') According to experiments made in the physiological laboratory of the Uni- 

 versity of Amsterdam. 



