The article by Dr. Sewall Wright discusses the importance of coefficients of inbreeding in the breeding of domestic animals, particularly in the context of consanguineous matings. Wright addresses the limitations of Pearl's coefficient, which can yield the same value for systems with different inbreeding effects. To overcome this, Wright introduces a partial inbreeding index that measures the percentage of inbreeding due to the relationship between the sire and dam. This index is designed to better reflect the actual effects of inbreeding on vigor and uniformity within the inbred stock. Wright explains that the decrease in vigor is attributed to the accumulation of recessive factors that are more likely to be harmful than dominant ones. He proposes a method to calculate the percentage of homozygosity, which is crucial for determining the inbreeding coefficient. The formula \(2h-1\) (or \(1-2p\)) is used to scale the coefficient from 0 to 1, where \(h\) is the proportion of complete homozygosity and \(p\) is the proportion of heterozygosity. The article also provides formulas for calculating the path coefficients and the correlation between individuals, which are essential for understanding the inbreeding in complex pedigrees. Wright illustrates these concepts with examples from real pedigrees, such as Roan Gauntlet and Comet, showing how the inbreeding coefficients can be calculated and compared across different systems of mating.The article by Dr. Sewall Wright discusses the importance of coefficients of inbreeding in the breeding of domestic animals, particularly in the context of consanguineous matings. Wright addresses the limitations of Pearl's coefficient, which can yield the same value for systems with different inbreeding effects. To overcome this, Wright introduces a partial inbreeding index that measures the percentage of inbreeding due to the relationship between the sire and dam. This index is designed to better reflect the actual effects of inbreeding on vigor and uniformity within the inbred stock. Wright explains that the decrease in vigor is attributed to the accumulation of recessive factors that are more likely to be harmful than dominant ones. He proposes a method to calculate the percentage of homozygosity, which is crucial for determining the inbreeding coefficient. The formula \(2h-1\) (or \(1-2p\)) is used to scale the coefficient from 0 to 1, where \(h\) is the proportion of complete homozygosity and \(p\) is the proportion of heterozygosity. The article also provides formulas for calculating the path coefficients and the correlation between individuals, which are essential for understanding the inbreeding in complex pedigrees. Wright illustrates these concepts with examples from real pedigrees, such as Roan Gauntlet and Comet, showing how the inbreeding coefficients can be calculated and compared across different systems of mating.