152 



NATURE 



[December 15, 1898 



unknown chemical nature, the products of muscular con- 

 traction, acting upon the medullarv- centres, or that they 

 are reflex ? In this latter case two hypotheses maybe 

 adopted —viz. that the afferent impulse is due to peri- 

 pheral chemical, or peripheral mechanical stimulation. 

 So far as I am aware no work has been done on the 

 lines of Geppert and Zuntz {loc. cit.\ or Filehne and 

 Kionka [Pjliigers Archives, 15d. Ixii, 201, 1S96) with 

 regard to the vascular effects of exercise. .A paralysing 

 action on motor nerve endings has been ascribed to the 

 products of muscular activity, but to what extent the 

 nerve endings in non-striped muscle are influenced by 

 these products has not been shown. A further question 

 of interest, which remains yet to be decided, is what are 

 the vascular areas which become anaemic during exercise ? 

 The nausea or vomiting, which is the frequent accom- 

 paniment of violent exercise when one is in "bad 

 condition," seems to point to the splanchnic area as the 

 one at the expense of which the muscular plethora 

 occurs ; but, so far as I am aware, no phlethysmographic 

 records of the abdominal organs during extensive 

 muscular contraction have as yet been made. 



In considering ttie effect of the contraction of a 

 muscle upon the circulation through it, the muscular 

 substance of the heart itself naturally comes into con- 

 sideration. The circulation through the coronary arteries 

 when these vessels have not lost their normal elasticity 

 from atheroma or other causes, is unquestionably in- 

 creased by full and frequent cardiac contraction, and 

 the state of nutrition of the heart thereby improved. 

 Further, increased pressure in the aorta within certain 

 limits is advantageous to the coronary circulation. The 

 experiments which have been made recently upon the 

 excised mammalian heart (Langendorf, PJiugers 

 Archh'es, Ixx., 1898, p. 473) tend to show that the 

 conditions for optimal contraction — that is, for a 

 maximum output of energy at each beat — are practic- 

 ally the same in the case of the mammalian as in 

 that of the frog's heart (Tunnicliffe, Journal 0/ P/iys., 

 XX. I, 96). Of these one of the most important is the 

 choice of an optimal load, the cardiac muscle in this 

 respect being similar to ordinary striped muscle. This, 

 from a practical standpoint, amounts to the fact that 

 although a heart can be, and of course very often is 

 overloaded, or in other words is unable to meet the 

 resistance which the normal circulation offers to its 

 contraction, it can also be underloaded ; that is, the cause 

 of its insufficient contraction may be that not sufficient 

 resistance is offered to its systole. This underloading 

 of the heart m.ay play an important rtVc in sluggish 

 circulations in women, and men living sedentary lives. 

 Fairly severe but gradually commenced and gradually 

 increased exercise in these individuals will often supply 

 the necessary load, and bring back the cardiac action to 

 the normal. It is the function of the physician to dis- 

 criminate between the over- and under-loaded heart, and 

 to treat it accordingly ; exercise may find a place in 

 each variety of this treatment. 



In this paper nothing has been said with regard to 

 another aspect of exercise from a therapeutic standpoint. 

 We have discussed the possibility of certain chemical 

 substances produced during the contraction of muscle 

 exerting an action on the respiratory and cardio-vascular 

 centres, but we have said nothing of the possible effect 

 on general metabolism of such products or others accom- 

 panying them. That such an effect is produced is seen 

 by the general nutritive results of local muscular exercise 

 and of massage. Whether the physiological basis of such 

 a result consists in the removal of waste products^that 

 is, is essentially increased excretion — or in the production 

 of substances which have an action allied to the internal 

 secretion of glands, remains yet to be decided. 



F. W. Tl'XNICI.lKFK. 



NO. 1520, VOL. 59] 



THE ZOOLOGICAL EXPLORATION OF THE 

 GREAT AFRICAN LAKES. 



/^WING to the unique and extremely interesting nature 

 ^^ of the fauna in Lake Tanganyika, the study of which 

 was recently the object of an expedition supported by the 

 Royal Society, and led by Mr. J. E. S. Moore, a 

 Committee has been formed, consisting of Sir John Kirk, 

 G.C.M.G., K.C.B., F.k.S. (late British Resident at 

 Zanzibar), Dr. P. L. Sclater, F.R.S. (secretary to the 

 Zoological Society), Mr. Thiselton-Uyer, C.M.G., F.R.S. 

 (director of Kew Gardens), Prof. Ray Lankester, 

 F.R.S. (director of the Natural History Departments of 

 the British Museum), and Mr. G. .\. Boulenger, F.R.S. 

 (of the British Museum), for the purpose of organising 

 another expedition to the same regions, to thoroughly 

 survey the basin, not only of Lake langanyika, but also 

 the unknown portions of the northern extension of the 

 great series of valleys in which Tanganyika, together with 

 Lakes Kivu andthe .-Xlbert Nyanza, lie : to collect specimens 

 of the aquatic fauna and flora, and to study the geological 

 history of this part of Africa. The latter object of the in- 

 vestigation should be of especial interest, for it was shown 

 by Mr. Moore that almost without exception the shells of 

 the singular series of whelk-like molluscs, captured by him 

 in Tanganyika, are indistinguishable from those now 

 found fossilised in Europe, among the remains of old 

 Jurassic seas. It would thus appear that at some remote 

 period of time, the great valley of Tanganyika was in 

 connection with the sea, and that the strangely isolated 

 marine fauna, which still inhabits its slightly brackish 

 waters, has remained there ever since. So far only the 

 Metiiisaf ijelly-fish!, the MollusM, and the Crustacea. 

 belonging to this antique fauna, have been discovered in 

 the lake ; but when its vast size and depth are fully 

 realised, it is unquestionable that by far the larger portion 

 of its fauna is as yet unknown. 



Tanganyika thus presents a unique field for scientific 

 e.xploration at the present time, and is, indeed, one of 

 the few places now left upon the earth where animals 

 (like those peculiar to .Australia) which have long since 

 become extinct elsewhere, may still be found. 



Another notable fact ascertained during Mr. Moore's 

 last expedition, was that the marine, or Haloliinnic fauna 

 of Lake Tanganyika does not exist in either Xyassa or 

 in Lakes Shirwa, Mwero, Bangweolo, or any of the 

 remaining lakes about which anything zoological is 

 known ; but it may yet be found in Lakes Kivu, the .-Mbert 

 Edward and Alljert Nyanzas, which lie, as has been 

 said, in an extension of the same great depression which 

 contains the Dead .Sea towards the north. The prob- 

 ability of this being so, is also increased by the curious fact 

 that the fauna of Tanganyika bears some resemblance to 

 that of the lower i)ortions of the Nile. 



During the present expedition it is therefore intended 

 to go north from Tanganyika, which will form the zoo- 

 logical headquarters of the expedition, through the 

 unknown region which lies between Tanganyika and 

 Lake Kivu, on, finally, to the .Albert Edwaid and 

 Rowenzori districts. It is intended then that the ex- 

 pedition shall pass eastward, through the Uganda 

 stations north of the Victoria Nyanza, down the Uganda 

 roads and railway to the sea. Mr. Moore's previous ex- 

 pedition was hampered by the unexpected dithcultics of 

 transport and the want of a steamer properly to carry on 

 dredging and sounding operations in the lake, and, in 

 consequence of this, much valuable material, particularly 

 large specimens of entirely new species of fish, had to be 

 deliberately left liehind. At the present time, however, 

 the .African Lakes Corporation are running the London 

 Missionary Society's old steamer once more upon the lake, 

 and all these deficiencies can therefore now be overcome, 

 provided the necessary funds are raised. 



