THE EFFECT OF ENVIRONMENTAL POTASSIUM AND CALCIUM CONCENTRATIONS ON THE RECOVERY OF THE ACTION POTENTIAL AND RELATED FUNCTIONS OF NERVE

1. When the Ringer''s solution applied to isolated frog sciatic nerve contains K⁺ in concentrations greater than 2 x standard, the height of the spike and of the after-potential is decreased, as is the duration of the after-potential; recovery of height and of excitability following response is delayed; degree and duration of supernormal excitability are decreased; postcathodal depression and postanodal enhancement are increased and prolonged. 2. The nerve functions just listed in general all change in the opposite direction when exposed'' to increased environmental [Ca⁺⁺]. (4.5–20 x standard) or decreased [K⁺] (0.05–0.2 x standard). The effects of decreased [Ca⁺⁺] (0.20–0.25 x standard) are indeterminate. 3. When [K⁺] and [Ca⁺⁺] are both greater than 2 x standard, whatever the ratio between the concentrations the effects characteristic of high [K⁺] eventually predominate. However, these effects, except for those involving spike height, are preceded by effects characteristic of high [Ca⁺⁺] when this cation is present in sufficient excess. 4. When [K⁺] and [Ca⁺⁺] are reduced to equal low levels (0.1–0.2 x standard), effects characteristic of low [K⁺] and high [Ca⁺⁺] are obtained. 5. The experimentally determined order of ability of the environments to produce changes characteristic of high K⁺ (which is the reverse of the order of their ability to produce changes characteristic of high [Ca⁺⁺]), is not the order of their K⁺ or Ca⁺⁺ concentrations, nor of the ratio between these concentrations (Table II). 6. The results may be explained by the assumption that the functions investigated are all to greater or less degree controlled by (1) the [K⁺]/[Ca⁺⁺] ratio and (2) the K⁺ concentration, at least when this exceeds a critical level. Control by [K⁺] is more effective for spike height and its recovery after stimulation than for the other functions. The special rôle of K⁺ is attributed to an unknown specific effect of this ion which Ca⁺⁺ is unable to oppose. It is suggested that this K⁺ effect in general becomes marked on the frog nerve functions investigated when the K⁺ concentration is somewhat above 2 x standard, while the [K⁺]/[Ca⁺⁺] ratio must be changed by a factor of 4 or more before it exerts a definite effect on these functions. 7. In standard and in modified cationic environments, nerve functions vary in the ease with which they manifest changes characteristic of high [K⁺] or of high [Ca⁺⁺]. 8. The after-potential functions are less completely controlled by the cationic environment than are the other functions investigated.     

COMPARATIVE STUDIES ON RESPIRATION : XXV. THE ACTION OF CHLOROFORM ON THE OXIDATION OF SOME ORGANIC ACIDS.

1. Organic acids when treated with H₂O₂ and Fe₂(SO₄)₃ produce CO₂ at a rate that can be measured by the indicator method. 2. In the case of acids containing a double bond, the rate of production of CO₂ can be varied by the addition of an anesthetic. The changes in the rate of production of CO₂ under the influence of a typical anesthetic, such as chloroform, show a striking resemblance to the reaction of the organism.     

THE PHYSIOLOGICAL AND SEROLOGICAL PROPERTIES OF STREPTOCOCCUS BOVIS AND RELATED ORGANISMS ISOLATED FROM CATTLE AND SHEEP

The physiological and serological properties of 153 strains of Streptococcus bovis isolated from cattle and sheep have been studied. With 12 specific antisera it was possible to type 75 of the isolates. Neither the fermentation of arabinose nor of raffinose was related to type specificity. The only strain fermenting mannitol was serologically distinct from all the other strains, and the type antigen was probably located on the cell wall whereas with the other 11 types it was capsular.
The distribution of these types in cattle and sheep has been determined together with their changes in individual cows sampled on three occasions over 18 months.     

THE ANTI-ESTERASE ACTIVITY OF PARATHION AND SOME RELATED ORGANOPHOSPHORUS COMPOUNDS

The in vitro activity of cholinesterase and acetylesterase of two insect species- Locusta migratoria migratorioides R. &F. and Calandra granaria L.—has been examined.
There appear to be two distinct enzymes present, and in both insects their activities are at comparable levels and their inhibition by the organophosphorus compounds examined are also similar.
Compounds possessing the phosphoryl group have high inhibitory activity and those with the thiophosphoryl group have low activity in vitro.