56 



NA rURE 



'May 17, 1906 



off at one or other of the bars, showing these to be places 

 of weakness. 



The extent of the barring varies much on different birds 

 and according to locality and season. Sometimes all the 

 wing, tail, and covert feathers are affected, while in others 

 only a few plumes exhibit the imperfection. .Again, the 

 number of bars on different feathers varies greatly; 

 frequently they occur at fairly regular intervals along the 

 entire length of the feather, or only a few are present and 

 the rest of the feather is perfect. Where the barring is 

 close, a single barb will be irregular at five or six places 

 along its length. The deficiency can be overcome to a 

 large degree by juxtaposition in the process of " dressing " 

 before the feathers are retailed, but buyers estimate that, 

 as a result of the presence of the bars, the value of the 

 feather to the farmer is frequently diminished from 20 per 

 cent, to 50 per cent., probably an average of about 25 per 

 cent. As the trouble is very general over all the ostrich- 

 farming districts in South Africa, it is manifest that the 

 subject is one which calls for thorough scientific investi- 

 gation. 

 The development of the ostrich feather has not vet been 



Fig. 1.— Ostrich fe; 



.howiiig ba 



worked out, but from our knowledge of that of feathers 

 generally there can be no question that the barring re- 

 presents some interference with the normal growth o^ the 

 plume at an early stage, an interference which prevents 

 the proper differentiation later of the feather into rachis, 

 barbs, and barbules ; moreover, these must recur from time 

 to time during the growth of the feather. .As to the cause, 

 the evidence mainly points to impaired nutrition of the 

 feather germ during its early stages. Farmers universally 

 acknowledge that an insufficiency of food during the time 

 the feathers are forming, as from a drought, "will result 

 in a plucking full of barrings, breakages, and other mal- 

 formations. In a general way it is recognised that the 

 better fed the bird the less likely are its feathers to show- 

 any defects. Furthermore, from correspondence with Dr. 

 R. M. Strong, of the University of Chicago, who has been 

 engaged upon a study of the developmerit of feathers for 

 years, I learn that experiments have been conducted bv 

 Prof. C. O. Whitman and himself upon malformations in 

 other birds exactly similar to those of the ostrich. Ring- 



NO. 1907, VOL. 74] 



doves, after hatchmg, weic alternately starved and fed for 

 some days at a time when the feather was in process of 

 formation, with very remarkable results. On the feathers 

 developing, similar bars were produced in verv striking 

 fashion and in great profusion. The results of the experi- 

 ments were such as to leave no doubt that the barring in 

 this case was due to malnutrition or some disturbance in 

 the metabolism of the bird. 



The ostrich farmer, however, is convinced that in- 

 sufficiency of food is not the only factor involved. Fre- 

 quently bars appear on the feathers of birds which appar- 

 ently have been well fed all the time. A general opinion 

 prevails that the ostrich fly, Hippobosca stnithionis, is 

 often responsible for the trouble, and also the ostrich mite, 

 Pterolichus bicandalns, both of which sometimes infest the 

 birds in large numbers. It is difficult to see how these 

 external parasites can act directly upon the feather germ, 

 but it is undoubted that the progressive farmer who dips 

 or sprays his birds against the pests produces a plumage 

 . much less subject to imperfections, and consequently of 

 higher value. Whether the fly or mite can affect the 

 feather directly or only indirectly by lowering the general 

 condition of health of the bird is a subject for investigation, 

 as is also the influence of the tape-worms and Ihrcad-worms 

 iStrongyhis douglassi) which frequently infest the animals. 

 The influence of in-breeding and heredity will also have 

 to be considered. It is significant to find that a similar 

 barring occurs on the ostrich farms in Pasadena, Cali- 

 fornia, among birds which have been ill fed, and the trouble 

 is general on the ostrich farms in Florida, where con- 

 ditions are not so favourable for birds. A much rarer 

 defect is where the parts of a feather have failed to differ- 

 entiate along one or more vertical lines extending the whole 

 length of the vane. This irregularity is in all probability 

 the result of some permanent injury to the feather germ 

 or its socket, and occurs independently of the nutritive 

 condition of the bird. 



The production of these irregularities in the growth of 

 feathers as epidermal derivatives is of much zoological 

 interest in connection with pathological conditions of 

 epidermal structures generally. As is well known, the 

 enamel of the teeth of children is frequently grooved or 

 pitted in transverse rows, a condition which can usually 

 be traced to some error in feeding, congenital disease, or 

 ailments affecting the general nutrition of the body during 

 the time the teeth were forming ; the finger nails are often 

 transversely grooved after an illness or injury, pointing to 

 a response to malnutrition ; hair frequently breaks, falls 

 off, or changes in character after an illness from the same 

 cause ; the horns of cattle and antelopes occasionally show 

 one or more narrow constrictions representing a diminu- 

 tion in the amount of horny material. All these defects 

 can be correlated with some low condition of health of the 

 animal at the time, and serve to establish that the imper- 

 fections in ihe feathers of ostriches are not an isolated 

 phenomenon, but, mutatis mutandis, can be compared with 

 imoerfections in the epidermal products of other vertebrates. 

 While it may be rash to predict before the experiments 

 in hand are completed, yet from the facts already known 

 there seems good reason for expecting that the trouble w'ill 

 be found to rest very largely with the farmer, and that 

 the remedy will be mainly a question of a proper and 

 regular supplv of food — not an easy matter in time of 

 droughts. Without question there exists an extremely 

 sensitive relationship between the production of a perfect 

 feather and the proper nutrition of the bird ; artificial 

 selection in breeding may also assist towards the production 

 of a strain in which the feathers are less influenced by 

 constitutional changes in the bird. J. E. Di'ERDEX. 



Rhodes I'niversity College, Grahamstown, 

 Cape Colony. 



Origin of the Term " Metabatic." 



My attention has been directed to the word metabatic as 

 relating to the transfer of energy. I should be much obliged 

 if anyone could give me information as to the author of 

 the term, the date of its introduction, or any scientific 

 paper in which it occurs in such form as to betoken its 

 exact meaning. Robert E. B.iynes. 



Christ Church, Oxford. 



