Septembek 27, 1907] 



SCIENCE 



415 



Protein Poisons: Victor C. Vaughan. 



The author has been able by diverse methods 

 to split proteins — bacterial, vegetable and 

 animal — into poisonous and non-poisonous 

 products. 



The poisons obtained from the different pro- 

 teins are similar, but are not identical. All 

 are soluble in both water and absolute alcohol, 

 more freely in the latter than in the former. 

 The aqueous solutions are acid and slowly 

 decompose sodium bicarbonate, forming salts, 

 apparently, and these are less poisonous than 

 the free acids. The aqueous solutions give 

 the general color reactions for proteins with 

 the exception of that of Moliseh, and some of 

 them give this reaction. However, most of 

 the protein poisons obtained by cleavage of 

 the protein molecule contain no carbohydrate 

 and are free from phosphorus. 



These poisons when injected into animals 

 intra-abdominally, subcutaneously or intra- 

 venously induce characteristic symptoms and 

 when administered in sufficient quantity kill 

 promptly. 



Death is due to failure of respiration and 

 the heart often continues to beat for some 

 minutes after respiration has ceased. It seems 

 most probable that death is due to the direct 

 action of the poisons on the respiratory center. 

 It is inferred from the readiness with which 

 recovery may follow non-fatal doses that the 

 poison cripples, but does not destroy, the cells 

 of the respiratory center. 



All attempts to produce antitoxins with 

 these protein poisons have, so far, failed. It 

 is true that repeated treatments of animals 

 with non-fatal doses of the poisons from the 

 colon and typhoid bacilli enable animals to 

 bear from two to four times the ordinarily 

 fatal doses of living cultures of these bacteria, 

 but this seems to be due to an increased resist- 

 ance rather than to a true immunity. This 

 condition is not specific and may be induced 

 by the poisons obtained from peptone or egg 

 white, as well as with that obtained by cleav- 

 age of the homologous bacterium. 



Attempts have been made to ascertain the 

 chemical constitution of the protein poisons 

 by splitting them up with mineral acids, but 



at present these experiments have not yielded 

 satisfactory knowledge, and work along this 

 line is being continued. The physiologic ac- 

 tion of the protein poisons leads to the 

 suspicion that they contain a neurin group, 

 but so far the author has not been able to 

 demonstrate the presence of such a radical. 



Olservaiions on the Living, Developing Nerve 



Fiber: Eoss G. Harrison. 



The immediate object of the author's ex- 

 periments was to devise a method by which the 

 end of a growing nerve could be brought under 

 direct observation while alive, in order that a 

 correct conception might be had regarding 

 what takes place as the fiber extends during 

 embryonic development from the nerve center 

 to the periphery. 



The method employed was to locate pieces 

 of embryonic tissue known to give rise to 

 nerve fibers, as, for example, the whole or 

 fragments of the medullary tube, or ectoderm 

 from the branchial region, and to observe 

 their further development. The pieces were 

 taken from frog embryos about 3 mm. long, 

 at which stage, i. e., shortly after the closure 

 of the medullary folds, there is no visible 

 differentiation of the nerve elements. After 

 carefully dissecting it out, the piece of tissue 

 is removed by a fine pipette to a cover slip, 

 upon which is a drop of lymph freshly drawn 

 from one of the lymph sacs of an adult frog. 

 The lymph clots very quickly, holding the 

 tissue in a fixed position. The cover slip is 

 then inverted over a hollow slide and the 

 rim sealed with paraffin. When reasonable 

 aseptic precautions are taken, tissues will live 

 under these conditions for a week and in 

 some cases specimens have been kept alive 

 for nearly four weeks. Such specimens may 

 be readily observed from day to day under 

 highly magnifying powers. 



While the cell aggregates, which make up 

 the different organs and organ-complexes of 

 the embryo, do not undergo normal trans- 

 formation in form, owing no doubt in part to 

 the abnormal conditions of mechanical tension 

 to which they are subjected, nevertheless, the 

 individual tissue elements do differentiate 

 characteristically. Groups of epidermal cells 



