THE RELATION OF CARBON DIOXIDE TO 



SPONTANEOUS MOVEMENTS IN THE 



LARV^: OF OPS AN US TAU. 



HENRY C. TRACY.' 



Spontaneous movements in embryos have been reported in 

 the literature since the time of William Harvey (1651). Such 

 movements have been observed in many groups of animals, and 

 their occurrence is probably a universal phenomenon. 2 



More or less definite statements as to a relation between 

 embryonic movements and respiratory conditions, have appeared 

 several times in the literature. 



Balfour ('76) says: "The band [of longitudinal striated 

 muscles] developed at this stage [II] appears to be a special 

 formation which has arisen through the action of natural selec- 

 tion, to enable the embryo to meet its respiratory requirements, 

 by continually moving about, and so subjecting its body to 

 fresh oxydizing influences; and as such affords an interesting 

 example of an important structure acquired during and for 

 embryonic life." 



Ahlfeld ('05) showed the existence of rhythmic movements in 

 the human fetus during the second half of pregnancy, manifested 

 by rhythmic undulations of the maternal abdominal wall. 

 These movements were near the rate of respiration in the new- 

 born and were interpreted as preliminary respiratory movements. 



Sarwey ('15) states that there is an increase in the strength 

 and frequency of foetal movements at the beginning of asphyxia 

 and shortly before death. 



Minkowski ('21) says: "On admet generalment que 1'asphyxie 

 de la mere mene a une augmentation des mouvements foetaux, 

 1'asphyxie directe du foetus pourrait done egalement le faire. 

 Le manque d'oxygene agirait alors com me une excitation inter- 



1 Contribution from the laboratory of the United States Bureau of Fisheries, 

 Woods Hole, Mass., and the Department of Anatomy, University of Kansas. 



2 References to the literature on these movements may be found in Preyer, '85; 

 Munkowski, '21, and Wintrebert, '20. 



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