Studies in Paleopathology 



38' 



of animals which have disappeared from 

 the earth. 2S 



I do not intend to assert that senility or 

 senescence is a disease, but that age weakens 

 the organism and the race and allows the 

 ingress of disease. Minot has stated: 



"Old age is not a disease and cannot be 

 cured; it is an accumulation of changes 

 which begin during earliest youth and 

 continue throughout the entire life of 

 the individual." 



It may be said that disease in the past 

 has often attacked the races of animals 

 which showed senescence. Many of the 

 virile races of animals in the past were also 

 subject to disease. The paleontological in- 

 dications of senescence are the reduction in 

 size, the loss of vigor and the production of 

 apparently useless spines as seen in the 

 races of animals which have become re- 

 duced or extinct, such as the crinoids, 

 trilobites, brachiopods, ammonites and the 

 dinosaurs. Other examples of senescence may 

 be seen among some of the Permian reptiles 

 which assumed bizarre forms. The tendency 

 of many races of animals to acquire spinous 

 and other useless excrescences of the hard 

 parts shortly before the extinction of the 

 group is noteworthy, and this tendency has 

 been regarded by paleontologists as an 

 indication of senescence. 



LESIONS OF PARASITISM IN CAR- 

 BONIFEROUS CRINOIDS 



Our knowledge of the history of disease, 

 as it is based on paleontological evidence, 

 begins with the Carboniferous, when cer- 



28 This suggestion has been discussed by Rene 

 Larger in his paper "La contre-evolution ou degen- 

 eresence par I'heredite pathologique cause naturelle 

 de ['extinction des groupes animaux. Essai de pale- 

 opathologique generate comparee," 1916, Bull, 

 et mem. Soc. d'anthrop. de Par. 



19 Graff: "Paleontographica," 1885, Bd. 31, pp. 

 183-192, Taf. xvi. 



tain crinoids were afflicted in their stems 

 with tumor-like lesions, possibly due to the 

 parasitic action of myzostomids such as 

 commonly attack crinoid stems today. A 

 careful description of the enlarged stems of 

 recent crinoids and the parasitic action ol 

 the myzostomids is to be found in the 

 reports of the Challenger Exploring Ex- 

 pedition. A comparison of the ancient and 

 recent lesions on the stems of crinoids leads 

 one to accept the enlargements of fossil 

 crinoid stems as due to the parasitic action 

 of the myzostomids or some similar form. 



The evidences for such a conclusion are, 

 apparently, incontrovertible, and have been 

 established by a number of writers on fossil 

 crinoids. Parasitized crinoid stems are 

 known from the Carboniferous of Scotland, 

 Germany (Fig. 1) and the Keokuk beds 

 (Fig. 4) of North America. Graff 29 found 

 the carbonized remains of the parasite in 

 one of the enlargements (Fig. 2) which he 

 studied and which he referred to as the 

 fossilized integument of the myzostomid. 

 The presence of this soft-bodied animal so 

 early in the geological history of the world 

 is not surprising, since from the researches 

 of Walcott 30 we know that jellyfishes, 

 sea cucumbers, many types of annulates, 

 and soft-bodied crustaceans lived during 

 the Cambrian, many millions of years 

 earlier. The parasitism of animals during 

 the Carboniferous was preceded by partial 

 parasitism or commensalism of the earlier 

 periods, and is known to have occurred 

 among fossil corals (Fig. 3) of the Devonian. 

 The intimate association of animals and the 

 origin of parasitism and commensalism dur- 

 ing the early part of the Paleozoic has been 

 studied by Clarke. 31 The reader is referred 

 to his paper for further details. 



30 C. D. Walcott: "Evidences of Primitive Life," 

 Smithsonian Rep. for 1Q15, pp. 235-255, with plates. 



31 John M. Clarke: "The Beginnings of Dependent 

 Life," Fourth Ann. Rep., Director 0/ Science Div., 

 New York State Education Dept., 1908, pp. 1-28. 

 PI. 1-13. 



