RELATION TO OTHER SCIENCES 131 



Especially numerous and close relations exist between pathology 

 and that branch of biology which treats of the development of the 

 human and animal body, and these relations are daily becoming 

 closer and more numerous, as more and more frequently it can be 

 proved or at least made probable, that pathologic phenomena of 

 all kinds form the basis of ontogenetic disturbances of the greatest 

 variation. 



An important difference exists between normal and pathologic 

 anatomy, in so far as the genetic consideration plays a much greater 

 role in the latter than in the former. Finished conditions form the 

 basis of descriptive anatomy. Pathologic anatomy must always 

 consider phases of development and none of its observations can be 

 understood if their origin cannot be explained and if the original 

 condition and the further development of its changes cannot be 

 determined. The original condition, however, leads more and more 

 frequently back to the time of embryonal development. It is to the 

 eternal merit of Joh. Fr. Meckel, 1 the anatomist and pathologist, 

 of Halle, that he showed for the first time in the case of a malforma- 

 tion of the intestinal diverticulum that the essential part of the varia- 

 tion from the normal consists in this, that a condition which is normal 

 for a certain period of embryonal life, but which should only have 

 a transient existence, is retained and is always recognizable in later 

 stages of development, even though changed by the progressive 

 growth of the part. This demonstration was the more important and 

 valuable, as it treated of a theme which had hitherto been the ground 

 of the most remarkable genetic theories. The apparently planless 

 variation from type was explained as the work of demons or devils 

 or as a freak of creative nature (lusus naturae). Now, it was shown 

 for the first time that also in the realm of malformations, order and 

 law governed the process and not arbitrariness and freakishness, and 

 that we must consider the embryonal development of these malfor- 

 mations if we would understand and explain these methodic processes. 



Thus was founded the doctrine of imperfect development and 

 growth, and as the basis for the explanation of malformations 

 (Hemmungs-Missbildungeri) it has been especially fruitful, as the 

 fissures about the face, malformations of the female genitals, and 

 congenital malformations of the heart will show, but that they have 

 not yet closed the list is shown by the recent investigations of cystic 

 kidneys, which have proved these to be due to a checking of the 

 development of the embryonal organs. These examples show that 

 disturbances of embryonal development are not only of importance 

 in causing variations from the type, such as malformations, but also 

 for disease-processes in the narrower sense, which originate most 

 readily in malformed parts or organs. The idea that congenital heart 



1 J. F. Meckel, Handb. d. pathol. Anat. i, p. 553. 



