The August Krogh principle has guided many comparative physiological studies, being especially useful for developmental physiology. Several attributes of unusual, if not unique, animals enable researchers to understand developmental phenomena more generally – the essence of the Krogh principle. This article provides examples of unusual traits of animals currently being used to understand development and reproduction. 1) Accelerated development greatly minimizes time spent examining how animals develop across time from egg to adult. For example, the tropical gar begins to breath air within as little as 2.5 days after hatching – much faster than other air-breathing fishes - facilitating study of the development of respiratory reflexes in fishes. 2) Transparency of the body wall has been exploited to image cardiac output in near-microscopic larvae of the zebrafish and mahi mahi, and to capitalize on bacterial biosensors to investigate development of in vivo digestive function in Caenorhabditis elegans. 3) Gigantism, as in the chicken-sized embryos of the emu, or the larvae of the paradoxical frog, allows surgeries not otherwise feasible. 4) Reproductive traits such as polyembryony in armadillos and parthenogenesis in planaria have informed us about classic gene vs. environment questions. Finally, 5) large body mass range enables clearer allometric analyses. Insects like the silk moth, show a more than a 1000-fold difference between eggs and adults. The August Krogh principle, then, is not simply to justify the study of exotic animals (as interesting as that is!), but has been used to generate a broader synthesis and understanding of all taxa.

奥古斯特·克罗格（August Krogh）原理指导了许多比较生理学研究，对发育生理学特别有用。异常动物（如果不是独特的话）的几个属性使研究人员能够更全面地理解发育现象-克罗格原理的本质。本文提供了一些动物的不寻常特征的示例，这些动物目前用于理解发育和繁殖。1）加速发育极大地减少了检查动物从卵到成虫的整个过程的时间。例如，热带雀在孵化后的2.5天内就开始呼吸空气，这比其他呼吸鱼类要快得多，这有助于研究鱼类呼吸反射的发展。2）车身壁的透明度已被利用来成像斑马鱼和ma鱼的近显微幼虫的心输出量，并利用细菌生物传感器研究秀丽隐杆线虫的体内消化功能的发展。3）巨人症，如in大小的鸡胚或自相矛盾的青蛙的幼虫，使得手术无法实现。4）生殖特性，例如犰狳中的多胚和平面虫中的孤雌生殖，已经使我们了解了经典的基因与环境问题。最后，5）大体重范围可以进行更清晰的异速分析。蚕蛾等昆虫在卵和成虫之间的差异超过1000倍。因此，奥古斯特·克罗格（August Krogh）原理不仅是为了证明研究外来动物的合理性（真是太有趣了！），而且还用于对所有分类单元进行更广泛的综合和理解。