With the conjunction “and” before “sloth,” the comma after “sloth” would not be needed, as “and” and the comma before it would give notice of the ending of the group.
The value of a comma in No. 79 is unmistakable; but is such punctuation helpful when the subject clearly ends itself, either because of its manifest completeness or because there is no apparent relation between the last word of the subject and the predicate verb? Probably a definite and satisfactory answer to this question cannot be given, for the mental capacity and alertness of the reader are involved.
DOUBTFUL MODIFIERS
Perhaps more obscurity in language, often resulting in hurtful misunderstandings and expensive litigation, grows out of doubtful modifiers than out of any other source of bad construction. A knowledge of punctuation here serves a very useful purpose, not always by putting the proper mark in the proper place, but generally by showing the writer the necessity of recasting his sentence, thus removing the cause of any possible wrong interpretation. Punctuation points out the danger; the writer removes it.
What did Smith write according to the wording and punctuation of the following sentence?
81. Smith wrote part of the preface and Chapter I.
It says clearly that Smith wrote part of the preface and part of Chapter I.
And what does the next sentence say he wrote?
81-1. Smith wrote part of the preface, and Chapter I.