68 



SCIENCE 



[N. S. Vol. XXV. No. 628 



tional departments of museums, to consider 

 the same idea, at least in the labeling of cer- 

 tain exhibits for specific classes of society 

 and for certain purposes? 



I do not recall ever having seen an exhibit 

 labeled in such a manner as to indicate that 

 a study had been made of " the art of ques- 

 tioning, by vchich the children " and the public 

 " are directed, inspired and attain the desired 

 mental grovpth. Telling the verong thing and 

 at the wrong time deadens interest and stunts 

 the child's powers. Whenever practicable, the 

 material should be observed first in its natural 

 environment." In such a museum depart- 

 ment the labels might describe that environ- 

 ment, giving the locality, etc., but leave the 

 visitor to make some discoveries. By a process 

 of this kind he would be forcibly impressed. 



I would not by any means suggest that 

 specimens in museums are over-labeled or 

 that the best forms of existing labels should 

 be set aside, but rather that if a few inter- 

 rogatory labels and exhibits were tried as an 

 experiment in a case or two, it might open 

 up a new line of possibilities to workers in 

 certain departments of museums and in some 

 kinds of museums. 



The quotations above are from a syllabus 

 on nature study for the primary grades for 

 normal college students by William Hittell 

 Sherzer, Ph.D. Harlan I. Smith 



Ameeioan Museum of Nattjkal History, 

 December 7, 1906 



SPECIAL ARTICLES 



NOTE ON THE COMPOSITION OF LIMULUS BLOOD 

 ASH 



Within recent years much attention has 

 been given by physiologists and pharmacolo- 

 gists to the chemical condition of automatic 

 tissues. It is generally conceded that a com- 

 plete knowledge of the chemical reactions go- 

 ing ffin in the tissues would go far towards 

 clearing up the mechanism of automatism. 

 The role played by the inorganic constituents 

 of the plasma has received particular atten- 

 tion. The principal organs used in the study 

 of automatism have been the heart and cili- 

 ated epithelium. Little work has been done 

 toward finding out to what extent the autom- 



atism of the ganglion cells depends on the 

 chemical changes going on in cells or in the 

 surrounding fluids during the activity of the 

 cells. The respiratory center in vertebrates is 

 not readily isolated for such study. Neither 

 can most of the work done on the vertebrate 

 heart be applied to the ganglion cells them- 

 selves, because in most of these experiments 

 the results are complicated by the simultane- 

 ous action of the chemicals on the heart 

 muscle.' 



This may account in part for the existence 

 of the two theories of the origin of the heart 

 beat. It may be that a more exact knowledge 

 of the chemical changes taking place in the 

 heart muscle, the ganglion cells and their sur- 

 rounding fluids, will explain the reason for 

 the existence of these divergent views. The 

 importance of data on the chemical reactions 

 taking place in the ganglion cells, especially 

 during activity, is obvious. Such data would 

 lead either to important generalizations or to 

 the refutation of generalizations already made. 



On account of its unique anatomy, the 

 Limulus heart ofl^ers the best organ known for 

 the study of ganglion automatism. The heart 

 may continue to beat rhythmically for days 

 after its removal from the body. The op- 

 timum temperature for keeping up this ac- 

 tivity is from 15° to 20° C. (Carlson). The 

 ganglion is easily dissected from the heart 

 without injuring its connections with the 

 heart muscle through its numerous nerves. 

 The heart thus serves as a delicate indicator 

 for the activity of the ganglion. 



Carlson'' has made use of this preparation 

 in the study of ganglion automatism. The 

 chemical phase of this investigation requires 

 a knowledge of the composition of the Limulus 

 blood plasma, particularly the inorganic con- 

 stituents. A qualitative and quantitative 

 analysis of the plasma during both rest and 

 activity, may give a better understanding of 

 the mechanism of automatism. If we find 

 that there are certain changes in the composi- 

 tion of the plasma during activity of the gan- 

 glion or heart muscle, we may conclude that 



' Carlson. Personal communication. 



' Carlson, A. J., Am. Journal Physiol., 1906, 

 XVI., p. 221; XVI., p. 378. 



