PREFACE. ix 



the truly natural system of birds. This idea he frequently expressed to me, when I still 

 resided in his immediate vicinity, but at the same time indicated that he by no means regarded 

 the natural sequence as the highest problem of the systematist, but rather the correct limitation 

 of the natural groups. To discover the latter was the aim of his investigations ; and with this 

 view everything was henceforward carried on, and every part of the bird's body carefully 

 examined. Nevertheless, he had always many deficiencies, especially as regards the muscular 

 structure of birds, which he only took up at a later period, and in the case of rare exotic species, 

 could investigate only on favorable occasions ; and the nervous system, upon which he left behind 

 him scarcely any observations, except a few outlines of the form of the brain. On the other 

 hand, he very accurately investigated the vascular system, especially after the year 1825. Of this 

 his Memoir on the Carotid Artery of Birds furnishes a proof. But as it is much more difficult 

 to procure materials for these anatomical observations after the indigenous species have been 

 examined than to investigate the skins, the purchase of which is necessary for the prescribed 

 increase of a zoological collection, the pterylographic side of his studies soon acquired a pre- 

 ponderance over the anatomical. This first appears to have led him to the idea of treating it by 

 itself, and of once more making a subject known in its entirety which had hitherto escaped 

 the notice of all ornithologists. Moreover, as he had passed his fiftieth year, the publication of 

 his materials might well appear to be the more necessary especially as frequent indispositions had 

 begun to shake his previously good health ; and these were reasons enough for his determination to 

 select a description of the arrangement of the feathers of birds as the subject of an academic thesis 

 which he had to prepare for the year 1833. This was completed under the title of ' Ptery- 

 lograpldcK Avium pars prior,' and was sent to several of his friends in single copies. Nitzsch 

 had already, no doubt, formed the plan of the whole work, and apparently had so arranged it that 

 a second part, containing the specialities, should be added to the first, the whole being elabo- 

 rated in Latin. He agreed upon this beforehand with the publisher, and arranged to have 

 several hundred additional copies of the first part printed at once. Indeed, he actually went to 

 work on the preparation of the second part, and made the drawings from which the last nine 

 plates of this work have been engraved. During the two years which were thus occupied, the 

 pterylographic materials, to which he now almost exclusively devoted all his spare time, had con- 

 siderably increased, and many of the statements already made in his published work had 

 thus come to require modification. This circumstance obstructed the completion of the work. 

 Nitzsch saw distinctly that it was not possible to attain accurate results from -existing materials, 

 and therefore thought it necessary to increase the latter at once. By this means he fell into a 

 condition of great hesitation, to which, indeed, he was always much inclined ; and just as he could 

 never decide upon having the first plate engraved, although the other nine had long been ready, 

 so he could never prevail upon himself to bring together the results of his observations and to 

 announce them as final. In such a frame of mind any elaboration of the text was, of course, 



